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Daphniola dionesp. nov., a valvatiform hydrobiid gastropod from Western Greece, is described based on conchological, anatomical and molecular data. D. dione is distinguished from the other species of the Greek endemic genus Daphniola by a unique combination of shell and soft body character states and by a 7–13% COI sequence divergence when compared to congeneric species. The only population of D. dione inhabits a cave spring on Lefkada Island, Ionian Sea.

This study reviews theDicharaxspecies in Thailand. Altogether tenDicharaxspecies are reported, four of which are new to science and described herein. They areDicharax borealisJirapatrasilp & Páll-Gergelysp. nov.,Dicharax burchiJirapatrasilp & Páll-Gergelysp. nov.,Dicharax panhaiJirapatrasilp & Páll-Gergelysp. nov.andDicharax pongratiJirapatrasilp & Tongkerdsp. nov.Alycaeus davisiGodwin-Austen, 1914 is regarded as a junior subjective synonym ofAlycaeus cucullatusTheobald, 1870 (=D. cucullatus) based on a similar depressed-conical shell shape, a long sutural tube and a sharp swelling behind the peristome. Furthermore, the type locality ofAlycaeus pratatensisPanha & Burch, 1997 (=D. pratatensis) had to be amended. Most important characters to distinguishDicharaxspecies are the general shell shape and relative lengths of teleoconch regions, whereas the spiral striation of R1, the shape of swelling of R3, the outer peristome crenulation and protrusion, and the exterior opercular sculpture show large intraspecific variability.

Lectotypification for Stellaria depressa Em. Schmid, S. yunnanensis Franch., S. ebracteata Kom., S. filicaulis Makino, and S. pusilla Em. Schmid are designated here.

Of the four species in the genus Cadlina present in the northwestern Pacific region, C. japonica has been the only species recorded from South Korea. For the purpose of investigating Cadlina in Korean waters, specimens were collected from the Korean East Sea (Sea of Japan) by scuba diving. The radula and morphology of these specimens were examined by stereoscopic and scanning electron microscopy. Based on morphology, three species were identified in Korean waters, including the new species, Cadlina koreanasp. nov., C. umiushi (first record in South Korea), and C. japonica. Cadlina koreanasp. nov. somewhat resembles C. umiushi but differs in both its morphology as well as the structure of its radula. The background color of Cadlina koreanasp. nov. is translucent white, tubercles on the dorsum are opaque white and the yellow marginal band is absent. The radular formula of Cadlina koreanasp. nov. is 57 × 23.1.23 with a rectangular rachidian tooth. In addition, mitochondrial cytochrome c subunit 1 (COI), 16S ribosomal RNA (16S rRNA), and nuclear 28S ribosomal RNA (28S rRNA) gene sequences were generated and used for analysis of Automatic Barcode Gap Discovery (ABGD) and reconstruction of the phylogenetic tree. Morphological distinction and genetic analyses confirm that three Cadlina species are present in Korean waters of which Cadlina koreana is a new species.

In this study, four new dextral camaenid from China are reported, based on shell morphology, reproductive system anatomy, and molecular phylogenetic analyses: Camaena funingensis Zhou, Wang & Lin, sp. nov., Camaena gaolongensis Zhou, Wang & Lin, sp. nov., Camaena maguanensis Zhou, Wang & Hu, sp. nov., and Camaena yulinensis Zhou, Wang & Hu, sp. nov. Detailed descriptions of the morphological characteristics including shells and genitalia, DNA sequences, and living environments of the four new species are provided, with further comparisons with congeners.

The genus Laoennea (Streptaxoidea, Diapheridae) was erected by Páll-Gergely, 2020. The type species, Laoennea carychioides Páll-Gergely, A. Reischütz & Maassen, 2020 is so far only known from the type locality cave in Laos. Herein, we describe a second species, Laoennea renouardisp. nov., from a nearby cave in the same karst region of Vientiane Province.

Specimens obtained from ten populations of a Monacha species from the central Apennines were compared with six molecular lineages of Monacha cantiana s. l. (CAN-1, CAN-2, CAN-3, CAN-4, CAN-5, CAN-6) and two other Monacha species (M. cartusiana and M. parumcincta), treated as outgroup, by molecular (nucleotide sequences of two mitochondrial COI and 16S rDNA as well as two nuclear ITS2 and H3 gene fragments) and morphological (shell and genital anatomy) analysis. The results strongly suggest that these populations represent a separate species for which two names are available: the older Helix pantanellii De Stefani, 1879 and the junior M. ruffoi Giusti, 1973. The nucleotide sequences created well separated clades on each phylogenetic tree. Genital anatomy included several distinctive features concerning vaginal appendix, penis, penial papilla and flagellum; instead, shell characters only enabled them to be distinguished from M. cartusiana and M. parumcincta. Remarkably, populations of M. pantanellii show high morphological variability. Shell variability mainly concerns size, some populations having very small dimensions. Genital variability shows a more intricate pattern of all anatomical parts, being higher as regards the vagina and vaginal appendix. Despite this morphological variability, the K2P distance range of COI sequences between populations is narrow (0.2–4.5%), if we consider all but three of the 53 sequences obtained. This research confirmed that the species of Monacha and their molecularly distinguished lineages can only occasionally be recognised morphologically and that they have significant inter- and intra-population variability. The possibility of using an overall approach, including shell, genital and molecular evidence, was taken in order to establish a reliable taxonomic setting.

A new species of Kerkia, K. briani Rysiewska & Osikowski, sp. nov. is described from the spring Polički Studenac Vrelo (Crkvina), adjacent to the Trebišnjica River (Bosnia and Herzegovina) collected with Bou-Rouch technique, pumped from an interstitial habitat 50 cm below the bottom of the spring. The shell, female reproductive organs, and the penis are described and illustrated. Mitochondrial cytochrome oxidase subunit I (COI) and nuclear histone H3 partial sequences confirm the distinctness of the new species, and molecularly based phylogenetic relationships of Kerkia are briefly presented.

Amphibolidae is one of the most abundant families of gastropods in estuarine environments of south-eastern Australia. However, the range limits of the species of Salinator, one of the family’s two genera in the region, remain unclear partly due to uncertainty of identifications based solely on shell morphology. Insufficient data have been collected to address questions regarding the genetic variability of any of the species of Salinator. Here, DNA sequences from a segment of the cytochrome c oxidase subunit I and 28S ribosomal RNA genes were collected to investigate the distribution and variation of the three Salinator species in the region, these being S. fragilis, S. rhamphidia and S. tecta. The results demonstrate a large range extension in S. rhamphidia and suggest that S. tecta may have limited distribution in Tasmania. In contrast to previously-studied estuarine Mollusca in the south-eastern coasts of the mainland and Tasmania, S. rhamphidia has regional differentiation. There is evidence of genetic disequilibrium within S. fragilis, suggesting that it may presently comprise contributions from two distinct sets of populations.

The genus Peronia Fleming, 1822 includes all the onchidiid slugs with dorsal gills. Its taxonomy is revised for the first time based on a large collection of fresh material from the entire Indo-West Pacific, from South Africa to Hawaii. Nine species are supported by mitochondrial (COI and 16S) and nuclear (ITS2 and 28S) sequences as well as comparative anatomy. All types available were examined and the nomenclatural status of each existing name in the genus is addressed. Of 31 Peronia species-group names available, 27 are regarded as invalid (twenty-one synonyms, sixteen of which are new, five nomina dubia, and one homonym), and four as valid: Peronia peronii (Cuvier, 1804), Peronia verruculata (Cuvier, 1830), Peronia platei (Hoffmann, 1928), and Peronia madagascariensis (Labbé, 1934a). Five new species names are created: P. griffithsi Dayrat & Goulding, sp. nov., P. okinawensis Dayrat & Goulding, sp. nov., P. setoensis Dayrat & Goulding, sp. nov., P. sydneyensis Dayrat & Goulding, sp. nov., and P. willani Dayrat & Goulding, sp. nov.Peronia species are cryptic externally but can be distinguished using internal characters, with the exception of P. platei and P. setoensis. The anatomy of most species is described in detail here for the first time. All the secondary literature is commented on and historical specimens from museum collections were also examined to better establish species distributions. The genus Peronia includes two species that are widespread across the Indo-West Pacific (P. verruculata and P. peronii) as well as endemic species: P. okinawensis and P. setoensis are endemic to Japan, and P. willani is endemic to Northern Territory, Australia. Many new geographical records are provided, as well as a key to the species using morphological traits.

A new parasitic species of eulimid gastropod, Haliella seisuimaruaesp. nov., is described from bathyal (728–978 m) waters off the Pacific coasts of Japan. It shows the closest resemblance to the type species H. stenostoma from the North Atlantic and Barents Sea in having a tall shell with an almost straight outer lip, but differs in having a junction of the parietal wall and columellar lip at 38% of the aperture height from the suture (33% in H. stenostoma), a slightly wider aperture and a more curved and extended columellar lip. The holotype of H. seisuimaruaesp. nov. was found attached to an irregular sea urchin, Brissopsis sp. cf. luzonica (Spatangoida: Brissidae). This represents the first direct observation of parasitic ecology and echinoderm host for the genus Haliella. A new replacement name, Eulima tsushimensisnom. nov., is proposed here for Eulima stenostoma A. Adams, 1861, which is preoccupied by Eulima stenostoma Jeffreys, 1858 (type of Haliella).

Phestilla subodiosussp. nov. (Nudibranchia: Trinchesiidae) is a novel species that feeds on corals in the genus Montipora (Scleractinia: Acroporidae) which are economically important in the aquarium industry. Nuclear-encoded H3, 28SC1-C2, and mitochondrial-encoded COI and 16S markers were sequenced. Phylogenetic analysis, Automatic Barcode Gap Discovery (ABGD), morphological data, and feeding specialization all support the designation of Phestilla subodiosussp. nov. as a distinct species. Although new to science, Phestilla subodiosussp. nov. had been extensively reported by aquarium hobbyists as a prolific pest over the past two decades. The species fell into a well-studied genus, which could facilitate research into its control in reef aquaria. Our phylogenetic analysis also revealed Tenellia chaetopterana formed a well-supported clade with Phestilla. Based upon a literature review, its original morphological description, and our phylogenetic hypothesis, we reclassified this species as Phestilla chaetopteranacomb. nov.

A new land snail species that represents a new genus is reported from Hubei, China. The snail has a conical shell with pits and/or granules on embryonic whorls and a smooth teleoconch with straight peristome. The head of the animal has a developed wart. The mantle lobe is only developed on the left side. At the front of the buccal mass there is no chitinous jaw that is without exception seen in Chinese camaenids. Its radular teeth are usually slender and tongue-shaped, not typical in bradybaenine snails. The genital system is typical of Bradybaeninae and is characterized by the absence of a membranous sac surrounding the terminal genitalia, penial caecum or flagellum; a well-developed penis sheath; a symmetrical dart sac apparatus; and one distally branched mucous gland. The new species Sinorachis baihu Wu & Chen, gen. and sp. nov., is assigned to the type species of the new genus, in which all the known Chinese Rachis species are included. Thereby, the new genus is composed of three species, namely Sinorachis onychinus (Heude), comb. nov., Sinorachis aureus (Heude), comb. nov. and the new species.

Otesiopsis Habe, 1946 is a land snail genus, which is known so far from Japan and Taiwan. Individuals of this genus were collected from Gageodo Island, South Korea. This is the first record of the genus Otesiopsis from this country. The individuals from Gageodo Island appear to be a new species because of their unique shell morphologies, while the details of their anatomy are still lacking. Further studies are encouraged to investigate the taxonomic and conservation status of the genus Otesiopsis in South Korea.

A new species, Onchidium melakense Dayrat & Goulding, sp. nov., is described, bringing the total to four known species in the genus Onchidium Buchannan, 1800. Onchidium melakense is a rare species with only nine individuals found at three mangrove sites in the Andaman Islands and the Strait of Malacca (western Peninsular Malaysia and eastern Sumatra). The new species is delineated based on mitochondrial (COI and 16S) and nuclear (ITS2 and 28S) DNA sequences as well as comparative anatomy. Each Onchidium species is characterized by a distinct color and can easily be identified in the field, even in the Strait of Malacca where there are three sympatric Onchidium species. An identification key is provided. In addition, Onchidium stuxbergi (Westerlund, 1883) is recorded for the first time from eastern Sumatra, and Onchidium pallidipes Tapparone-Canefri, 1889, of which the type material is described and illustrated here, is regarded as a new junior synonym of O. stuxbergi.

Since the time of the original description there have been no precise locality records in Cambodia ofBertia cambojiensis(Reeve, 1860) and it was believed to be extinct. In 2012, a joint Natural History Museum survey with Vietnamese colleagues rediscovered living populations of this huge sinistral helicoid snail in a protected area of southern Vietnam. The genitalia and radula morphology are re-assessed and type specimens of all recognised congeners are figured herein. The unique morphological characters of this species are a small and simple penis, well-developed amatorial organ complex that incorporates four amatorial organ ducts, a short gametolytic organ complex and spiked papilla, and radula morphology with unicuspid teeth. The type locality ofB. cambojiensis, which has been contentious, is determined here to be in the vicinity of ‘Brelum’, Vietnam, near the border with Cambodia. In addition, the nucleotide sequences of barcoding genes COI, 16SrRNA and 28S fragments were provided for further comparison.

Here, the clarification of the “type” status for Cyclophorus (Glossostylus) koboensis Godwin-Austen, 1915 catalogued by Nantarat et al. (2014) is corrected and briefly discussed.

Members of the small bivalve family Cyrenoididae inhabit brackish waters of the eastern and western Atlantic Ocean. Cyrenoida floridana (Dall, 1896) from the western Atlantic is poorly known aside from shell descriptions. A detailed shell and anatomical study of C. floridana is here presented and compared with available data for Cyrenidae and Glauconomidae, two families of closest relationship according to recent phylogenetic studies. The species is characterized by valves externally covered by thin light brown periostracum; muscle scars and pallial line (without sinus) weakly impressed on the internal shell surface; a unique hinge pattern composed of cardinal and lateral teeth joining each other, right hinge with two laterals and two cardinals forming two inverted-V-shaped teeth and left hinge with two cardinals and one lateral forming a horizontal reversed F-shaped tooth; and microtubules inside the shell walls. Anatomically, the species presents unequal adductor muscles; demibranchs fused to each other along their posterior ends; a pair of totally fused, pigmented siphons; two pairs of siphonal retractor muscles; and a stomach with conjoined style sac and intestine, a single typhlosole, and three sorting areas. Evidence of shell parasitism is described.

The generic allocation of Helix subaperta is clarified by using genetic data and morphological traits of the genital organs; its position within the hitherto monotypic genus Cantareus is corroborated. Further analysis of several specimens of Cantareus apertus from Algeria and Italy revealed that this taxon is composed of two species, C. apertus from Italy, and C. koraegaelius from Algeria. The morphological traits of the genital organs of all three species are discussed, and the definition of the genus Cantareus is amended. All three species confined to Cantareus are re-described, and the syntype specimen of H. aperta is illustrated.

Invasive species of Pomacea snails are of growing concern when it comes to the conservation of global biodiversity. Pomacea canaliculata has been listed among the world’s 100 worst invasive species. In this work, phylogeographic patterns and the demographic history of P. canaliculata and P. maculata from different countries were analyzed using mtDNA cytochrome c oxidase subunit-I (COI) sequences. The results showed that P. canaliculata and P. maculata had high genetic diversity, significant genetic differentiation, limited gene flow and stable population dynamics among different countries. Genetic diversity of P. canaliculata was higher than P. maculata. Our study will also provide important information for the effective prevention and control of the spread of Pomacea snails.

As part of an ongoing effort to revise the taxonomy of air-breathing, marine, onchidiid slugs, a new genus, Laspionchis Dayrat & Goulding, gen. nov., is described from the mangroves of South-East Asia. It includes two new species, Laspionchis boucheti Dayrat & Goulding, sp. nov., and Laspionchis bourkei Dayrat & Goulding, sp. nov., both distributed from the Malacca Strait to the Philippines and Australia. This study is based on extensive field work in South-East Asia, comparative anatomy, and both mitochondrial (COI and 16S) and nuclear (ITS2 and 28S) DNA sequences. The two new species are found in the same habitat (mud surface in mangrove forests) and are externally cryptic but are distinct anatomically. Both species are also strongly supported by DNA sequences. Three cryptic, least-inclusive, reciprocally-monophyletic units within Laspionchis bourkei are regarded as subspecies: L. bourkei bourkei Dayrat & Goulding, ssp. nov., L. bourkei lateriensis Dayrat & Goulding, ssp. nov., and L. bourkei matangensis Dayrat & Goulding, ssp. nov. The present contribution shows again that species delineation is greatly enhanced by considering comparative anatomy and nuclear DNA sequences in addition to mitochondrial DNA sequences, and that thorough taxonomic revisions are the best and most efficient path to accurate biodiversity knowledge.

The taxonomy of the speciose genusGanesellaW.T. Blanford, 1863 and the endemic genusGlobotrochusHaas, 1935 is unclear since the anatomical characters of the the type species of these two genera have never been reported before. Therefore, the present paper provides the first anatomical descriptions of the reproductive apparatus, pallial system and radula ofHelix capitiumBenson, 1848 andHelix onesteraMabille, 1887, the respective type species ofGanesellaandGlobotrochus. In addition,Ganesella rhombostoma(Pfeiffer, 1861) andGanesella carinella(Möllendorff, 1902) from Thailand are re-described, and a new species,Ganesella halabalahSutcharit & Panha,sp. nov., from southern Thailand is described. This new species differs from all others by having a larger shell, an obtuse apex and an aperture lip with a prominent beak-like deflection.

A new and the first proven oxychilid species endemic to China is reported from Sichuan Province. Sinoxychilusgen. nov. is established based on this new species and has diagnostic traits of the sculptured protoconch, partial epiphallus wrapped by developed penis sheath, penial retractor muscle inserting on the top of penial caecum, spinelets on penial pilasters, absence of epiphallic papilla and perivaginal gland present on vagina and proximal bursa copulatrix duct. In light of shell morphology and through geometric morphometric analyses, Zonites scrobiculatus scrobiculatus Gredler and Z. scrobiculatus hupeina Gredler are proposed to be included in the new genus. A phylogenetic inference based on ITS2 gene indicates that the new genus is systematically close to Oxychilus Fitzinger, which is known from the Western Palearctic and the Southwestern Arabian Peninsula, regions that are geographically far from the distribution range of the new genus.

A characteristic feature shared by all Margaritiferidae mussels consists in the presence of scars on the internal surface of their shells. These scars mark places of mantle attachment by specific epithelial cells. According to some authors, such parameters of mantle attachment scars as the density and degree of their manifestation can be used for the purposes of species identification. To this end, quality indicators (numerous or few, pronounced or poorly visible scars) are typically used; however, the use of quantitative criteria is preferable. This work was aimed at developing quantitative indicators of mantle attachment scars in the Margaritifera margaritifera freshwater pearl mussels for the populations of the Syuskyuyanyoki and Livoyoki rivers (Karelia). It is shown that the density and size of mantle attachment scars are approximately the same for all the investigated shell samples. These parameters display the absence of dependence on the age and size of molluscs. The regression coefficients for the linear dependence of the density or size of mantle attachment scars on the age or length of the shell show no significant difference from 0. For all the investigated molluscs, the density and size of mantle attachment scars are established to vary within the range of 0.37–1.16 scars/cm2 (0.71 ± 0.03 scars/cm2 on average) and 215–690 µm (417 ± 2 µm on average), respectively. According to a two-factor analysis of variance, the distribution of mantle attachment scars appears to be irregular across the shell surface. At the same time, a significant (p < 0.001) increase in their density is observed in the posterior and ventral directions, as well as diagonally in the posterior ventral direction. Issues associated with the application of the investigated parameters for the purposes of mollusc species identification are discussed.

This paper defines a new crown clade Neostromboidea to separate the Strombidae, Rostellariidae, and Seraphsidae from their sister families Struthiolariidae and Aporrhaidae. There is significant value to understanding evolutionary processes within Stromboidea to recognise the universal similarity in the position of the eye on the end of peduncles and a diminished cephalic tentacle that arises from the middle to the end on that peduncle. This is in contrast to other members of the Stromboidea where the eye is located at the base of the cephalic tentacle. These physiological differences represent two set of organisms with divergent and independent evolutionary life histories and therefore these differences need to be identifiable within the nomenclature to bring meaning to the way we name things.

This nomenclator provides bibliographic details on all names in the family-, genus-, and species-group of the the family Paludomidae. All nomenclaturally available names are discussed including junior homonyms and objective junior synonyms as well as unavailable names such as nomina nuda, infrasubspecific names and, to some extent, also incorrect subsequent spellings. In the family-group a total of 28 names are included in the nomenclator, of which 21 are available and seven unavailable names. Of the available names in the family-group, six are invalid for nomenclatural reasons. In the genus-group a total of 57 names are included in the catalogue. Of the available names in the genus-group, 11 are invalid for nomenclatural reasons. In the species-group a total of 499 names are included, of which 463 are available, but 21 are invalid for nomenclatural reasons. All names are given in their original combination and spelling (mandatory changes are discussed and corrected spellings are provided), along with the reference to the original publication. For each family- and genus-group name, the original classification and the type genus or type species, respectively, are given. For species-group taxa the type locality and type horizon (for fossil taxa) are provided, usually as given in the original publication. A new name,Cleopatraadaminom. nov., is proposed for the fossilCleopatracylindrica(Adam, 1957), which is a homonym ofCleopatracridlandicylindricaMandahl-Barth, 1954, and a lectotype forCleopatradubiaAdam, 1959 is designated. A new replacement nameLeloupiellanom. nov. is proposed forStormsiaLeloup, 1953 which is a homonym ofStormsiaBourguignat, 1891.

This study presents new insights in the anatomy of genital organs of some large helicid gastropods from northern Africa. The genetic analysis with the markers COI, 16S, H3, and 5.8 S rRNA+ITS2 reveales a high support for Alabastrina and Otala as separate evolutionary lineages within the Otalini. The position of Siretia as another separate lineage within the Otalini is discussed. “Tingitanaminetteidecussata” clusters within the O.xanthodon clade and confirms that the genus Tingitana can be synonymised with Otala. The genus Alabastrina differs from all other known genera by possession of a penial appendix. This character state is also found in topotypic A.tistutensis. Examination of the twin penial papilla system in Otala recovers a reduction of the proximal penial papilla in O.punctata. The position of Helixmurcica as a separate subspecies of O.lactea is not supported, and it is here considered to be a synonym of the latter species.

The genera Aulacospira and Pseudostreptaxis of the Philippines are revised based on the collections of the Senckenberg Forschungsinstitut und Naturmuseum (Frankfurt am Main, Germany), the Florida Museum of Natural History (USA), and recently collected material. Three new species are described: Aulacospiralens Páll-Gergely & Auffenberg, sp. n., Aulacospirakrobyloides Páll-Gergely & Schilthuizen, sp. n., Pseudostreptaxisharli Páll-Gergely & Schilthuizen, sp. n.

Enneanigeriensissp. n. is described from southeastern Nigeria on the basis of external and internal shell morphology. Following Pilsbry’s formal criteria of a single palatal fold and corresponding external furrow, the new species may be assigned to Parennea. Enneanigeriensissp. n. exhibits substantial similarity with E.serrata, a species from Cameroon, in the cylindrical shell shape, crenulate suture, and internal shell morphology, indicating that the two species are closely related. CT scanning confirmed the presence of only a single palatal fold in E.nigeriensissp. n. and two in E.serrata. In spite of this, the Nigerian species is provisionally assigned to Ennea rather than Parennea, suggesting that the characters used to define Ennea and Parennea are insufficient to delimit natural groups of species. The holotype of E.serrata is examined for the first time since its description in 1896 and a redescription of the species is provided based on the two shells hitherto known. Study of the original specimens recorded as Ptychotrema (Parennea) sulciferum by Degner from Liberia reveals these to belong to Enneacf.thompsonae. The Nigerian shell recorded by van Bruggen as Ptychotrema (Parennea) aequatoriale proved to be a specimen of Enneacf.perforata. As a result, no species attributable to Parennea now appear to be known in West Africa; in contrast, numerous species are known from central and eastern Africa.

This paper describes a new genus, two new species and new records of subterranean gastropods from the Sabinas and Álamos River, Coahuila, and the Nazas River, Durango, in northern Mexico. Phreatomascogosgregoigen. n. et sp. n. from Don Martín Basin, Coahuila, is described based on shells and opercula that show some morphological similarities with shells of Phreatodrobia Hershler & Longley, 1986 (Lithoglyphidae), which is a subterranean genus from neighboring area in Texas, United States. Conchologically, the new genus can be distinguished from Phreatodrobia and all other subterranean genera by a unique combination of characteristic shell morphology and opercula apomorphies. Balconorbissabinasensesp. n. (Cochliopidae) is the second species of this genus, which was previously known only from caves and associated subterranean habitats in Texas. The new record of Coahuilixparrasense, Czaja, Estrada-Rodríguez, Romero-Méndez, Ávila-Rodríguez, Meza-Sánchez & Covich, 2017 (Cochliopidae) from Durango and Coahuila is the first record of extant member of this genus out of its hitherto known habitat in the Cuatro Ciénegas basin, Coahuila. These records are remarkable because C.parrasense had been described recently as a fossil species. Shell morphologies of the new subterranean snails could be interpreted as possible evolutional adaptations to different hydrodynamic and other specific conditions in their habitat.

Chrysopetalids, more specifically the subfamily Chrysopetalinae, are known for their characteristic, flattened, leaf-like notopodial chaetae. In many chrysopetalid species the animal’s body is dorsally covered by these paleae that are arranged in rows similar to the blades of a folding fan. In this study we investigate and compare the chaetal arrangement in two chrysopetalids: Bhawania goodei Webster, 1884 and Chrysopetalum cf. occidentale Johnson, 1897, using serial sectioning and 3D models. Our results reveal details on the topology of the chaetal formative site, where chaetogenesis occurs continuously. The course of chaetogenesis is significantly affected by the very large size of the chaetae, but nevertheless follows the general pattern of chaetogenesis in Annelida. Ultrastructure of the paleae confirms previous observations. The results of the study are the first on chaetogenesis and chaetal topology in a representative of the Phyllodocida. They indicate differences in the number of formative sites in neuro- and notopodia that now need to be studied in a larger number phyllodocid taxa. A special focus has been laid on details of paleal formation to study potential phylogenetic affinities between Wiwaxia and Chrysopetalidae that were proposed due to the significant similarity of the paleae to the sclerites of Wiwaxia.

Morphological and molecular data are presented for the first time in an integrative way for the genus Myja Bergh, 1896. In accordance with the new molecular phylogenies, the traditional Facelinidae is paraphyletic. Herein is presented the phylogenetic placement of true Facelinidae s. str., including the first molecular data for F.auriculata (Müller, 1776), type species of the genus Facelina Alder & Hancock, 1855. The taxonomic history of F.auriculata is reviewed. The genus Myja is related to the clade Facelinidae s. str., but shows disparate morphological traits. Two new species of the genus Myja, M.karinsp. n., and M.hyotansp. n., are described from the Pacific waters of Japan (middle Honshu), and M.cf.longicornis Bergh, 1896 is investigated from Thailand. According to molecular analysis and review of available morphological information, the genus Myja contains more hidden diversity. The family-level relationship within aeolidacean nudibranchs with emphasis on the family Facelinidae is outlined. The problem of the relationship between Facelinidae Bergh, 1889 and Glaucidae Gray, 1827 is discussed. The family Glaucidae has precedence over Facelinidae and is phylogenetically related to the core group of Facelinidae s. str., but has a profoundly modified aberrant external morphology, thus making a purely molecular-based approach to the taxonomy an unsatisfactory solution. To accommodate recently discovered hidden diversity within glaucids, the genus Glaucilla Bergh, 1861 is restored. The family Facelinidae s. str. is separate from, and not closely related to, a clade containing the genera Dondice Marcus, 1958, Godiva MacNae 1954, Hermissenda Bergh, 1879, and Phyllodesmium Ehrenberg, 1831 (= Myrrhine Bergh, 1905). The oldest valid available name for the separate ex-facelinid paraphyletic clade that contains several facelinid genera is Myrrhinidae Bergh, 1905, and resurrection of this family name under provision of the ICZN article 40.1 can preliminarily solve the problem of paraphyly of the traditional Facelinidae. “Facelinidae” s. l. needs to be further divided into several separate families, pending further study.

Two new lineages CAN-5 and CAN-6 were recognised in four populations of Monachacantiana (Montagu, 1803) s.l. from the Italian Apuan Alps by joint molecular and morphological analysis. They are different from other M.cantiana lineages known from English, Italian, Austrian and French populations, i.e. CAN-1, CAN-2, CAN-3 and CAN-4, as well as from the other Italian Monacha species used for comparisons (M.parumcincta and M.cartusiana). Although a definite taxonomic and nomenclatural setting seems to be premature, we suggest that the name or names for these new lineages as one or two species should be found among 19th century names (Helixsobara Mabille, 1881, H.ardesa Mabille, 1881, H.apuanica Mabille, 1881, H.carfaniensis De Stefani, 1883 and H.spallanzanii De Stefani, 1884).

Atlantid heteropods are a family of holoplanktonic marine gastropods that occur primarily in tropical and subtropical latitudes. Atlantids bear a delicate aragonitic shell (Atlanta brunneagroup. Results identify a new species,Atlanta vanderspoeli, from the Equatorial and South Pacific Ocean, and suggest that individuals ofA. brunnealiving in the Atlantic Ocean are an incipient species. Our results provide an important advance in atlantid taxonomy and will enable identification of these species in future studies of living and fossil plankton.

Background In this study, we clarify the classification of museum specimens of the family Viviparidae , which is composed of six species/subspecies in Japan, including three endangered species. We examined Viviparus sclateri specimens from the Tomotaro Iwakawa collection (1855-1933) in the National Museum of Nature and Science, Tokyo. The Iwakawa's collection was catalogued in 1919 and Viviparus sclateri , labelled with Naga-tanishi, the current Japanese name for H. longispira , which was, at the time, equivalent to Viviparus sclateri , was listed in this catalogue. The catalogue noted localities of Viviparus sclateri (Naga-tanishi) from outside Lake Biwa, including occurrences in Lake Kasumigaura and Lake Suwa. However, Heterogen longispira (Naga-tanishi) is currently considered to be endemic to Lake Biwa drainage. The actual status of Viviparus sclateri in Iwakawa (1919) has not been clarified until now. New information Our examination revealed that Viviparus sclateri from Iwakawa’s catalogue included H. japonica , H. longispira and Sinotaia quadrata histrica , based on current taxonomy. Specimens assigned to H. longispira occurred only in Lake Biwa drainage. Heterogen japonica was confirmed to be present in all lots and some H. japonica from Lake Suwa had a distinctive morphology. Sinotaia quadrata histrica was only confirmed to occur in Lake Suwa. Furthermore, some specimens from southern Lake Biwa and the Seta River had intermediate characteristics between H. japonica and H. longispira and their populations are currently almost extinct.

Several individuals of the terrestrial slug Deroceras laeve were collected in 2018 in the Hoàng Liên Son mountain range of northern Vietnam. The three specimens which were investigated anatomically were aphallic or hemiphallic. A partial COI sequence verified the species identity. This is the first discovery of D. laeve and also of the slug family Agriolimacidae on the Indochinese Peninsula. The collecting site is situated near a cable-car station and below a tourist complex on Fansipan mountain, both of which had just been built by a Swiss-Austrian company between 2013 and 2016. This and the fact that the species had not been found elsewhere in the surrounding area, although searched for thoroughly, indicate that D. laeve is most probably a recent introduction, potentially with building material from Austria or Switzerland.

The cerithioidSupplanaxis nucleus(Bruguière, 1789) is widespread in the Caribbean, where it lives in often dense aggregates on hard surfaces in the middle-high intertidal. Molecular evidence shows that it comprises two species that are in fact morphologically diagnosable. We fix the nomenclature ofSupplanaxis nucleusby designating a sequenced neotype from Bruguière’s historical locality of Barbados, and identify the second, cryptic species asS. nancyae(Petuch, 2013). The two live syntopically across the Caribbean and form a closely related species group with the PanamicS. planicostatus(G.B. Sowerby I, 1825).Planaxis nucleolaMörch, 1876, described from St Croix, in the Virgin Islands, never again recorded in the literature but listed as a synonym ofS. nucleusin taxonomic authority lists, is recognized as a valid species ofHineaGray, 1847.ProplanaxisThiele, 1929 andSupplanaxisThiele, 1929, are synonyms and the latter is given precedence over the former.

Thai terrestrial microsnails in the genus Aulacospira Möllendorff, 1890 are revised based on the collection of the Zoological Research Collection, Burapha University, Chonburi Province, Thailand and recently collected material. Three new species are described: Aulacospira nutadhirai sp.nov. from Southern Thailand, and Aulacospira tekavongaesp.nov. and Aulacospira vanwalleghemisp. nov. from Eastern Thailand. The radula and genital system are described, and a key to Thai species is presented.

Land snail surveys conducted in northern Laos between 2013 and 2014 have led to the discovery of a living population of Trichelix horrida (Pfeiffer, 1863). This species has never been recorded from specimens other than the types, and its distribution and anatomy have remained essentially unknown. The genitalia and radula morphology are documented here for the first time and employed to re-assess the systematic position of this species: the unique morphological characters of T. horrida are a penis similar in length to the vagina, a small and triangular penial verge, gametolytic organs extending as far as the albumen gland, head wart present, and unicuspid triangular radula teeth. The type locality of this species was believed to be from “Lao Mountains, Camboja,” and is restricted herein to be Luang Phrabang Province, northern Laos. The assignment of species to either of three genera, Trichelix Ancey, 1887, Moellendorffia Ancey, 1887, and Moellendorffiella Pilsbry, 1905, based solely on information provided in their original descriptions is difficult. The type specimens of all nominal species presently placed in either of these three genera are examined and illustrated herein. Comparison with the primary type specimens will assist future revisions aiming to resolve the systematics of these taxa. In addition, we transfer Moellendorffia faberiana (Möllendorff, 1888) to the genus Moellendorffiella.

Two new species, Sinoarinia feii Chen, gen. et sp. nov. and Pincerna vallis Chen & Wu, sp. nov., are described from western Hubei, China. The new genus Sinoarinia Chen & Wu, gen. nov. is established based on the strongly constricted penultimate whorl and the ascending last whorl. The Vietnamese species Pincerna costulosa (Bavay & Dautzenberg) is newly reported from Yunnan, China. For comparison, photographs of the shells of closely related species are provided. A key to the known species of Sinoariniagen. nov. is included.

Shells of the Rissooidea species that are known from Bhutan are characterized. Tricula montana is reported from that country for the first time. Two Erhaia species from Bhutan are described as new to science, viz. E. janneisp. nov., and E. pelkiaesp. nov., The holotypes of the Erhaia species that were described from Nepal are figured with photographs for the first time and compared with the congeneric taxa from Bhutan and India. Erhaia nainitalensis is considered a senior synonym of E. chandeshwariensis. An identification key is presented for the Erhaia species of the Himalayan foothills.

Research in recent years have provided rapid advances in biogeographic and taxonomic documentation of sea slugs around the world. However, efforts are lacking in surveying most coastlines and habitats in South-East Asia. Recent studies from the Gulf of Thailand have indicated that a wealth of unexplored sea slug diversity and ecology may be gained from an investigation of soft sediment habitats beyond the reef slopes. Additionally, the waters of Koh Tao have been found to host regionally high levels of sea slug diversity with several species awaiting taxonomic clarification. In this work the initial findings of an expanded survey effort from the waters around Koh Tao are provided, with the identity of two soft sediment-associated sacoglossan species in the family Plakobranchidae being investigated. By integrating morphological and molecular analyses, the species Plakobranchus noctisstellatus sp. nov. and Elysia aowthai sp. nov. are described and species complexes surrounding Plakobranchus ocellatus van Hasselt, 1824 and Elysia japonica Eliot, 1913 are discussed. The topics of morphological variability and the cryptic species problem are also discussed.