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Limpets up to at least 200 mm long occur widely in New Zealand early Haumurian (Campanian) rocks. Three specimens are in life position, attached to articulated specimens ofIsognomon. The limpet has several unique characters — an apparently anterior marginal apex (all gastropod limpets have a central or posterior apex), an enormously thickened apical area, and a tongue-like projection, with a gape at each side, below the margin at the anterior — demonstrating that it belongs inGigantocapulus Hayami & Kanie. The low shape, weak sculpture, and marginal apex indicate that it belongs inG. problematicus (Nagao & Otatume), previously reponed only from Japan and Kamchatka. New Zealand material supports previous interpretations that the apex was anterior, and thatGigantocapulus was an epiparasite or, more probably, a filter feeder living sedentarily on bivalves. The shell is, uniquely, composed of calcite in multiple complex crossed-lamellar layers, very different from the aragonite shell with inner nacreous and outer prismatic layers of both early Palaeozoic and present-day tergomyans. Nevertheless, as the anteriori?) tongue-like projection, thickening and gapes closely resemble those of early Palaeozoic tergomyans, no other limpet-shaped molluscs are known with an anterior apex, and not all modem monoplacophorans are minute (Neopilina reaches at least 40 mm long), a position in Monoplacophora (= Tergomya) remains a possibility. However,G. giganteus (Schmidt) has a subcentral apex and is clearly cyclomyan rather than tergomyan.Gigantocapulus is probably a vanikoroidean gastropod, but could also be a tergomyan, a helcionelloidan, or a member of another, now extinct group of gastropods. Gigantocapulidae n. fam. is proposed.

The anatomy of the neopilinid limpet Laevipilina antarctica is described on the basis of reconstructions of semithin serial section. In general the anatomy of this small (3.2 mm) species resembles those of Neopilina galatheae (37 mm) and Vema ewingi (27 mm); small differences occur in the alimentary tract. Corrections of the original descriptions of neopilinid anatomy concern the structure of the mantle margin, the presence and interpretation of cephalic appendages, and details of the nervous system. The excretory organs are clearly separated from each other and there is no connection with the pericardium. The neopilinid ctenidia are considered as ventilatory rather than respiratory organs. These corrections and clarifications of the neopilinid anatomy provide an improved database for discussion on monoplacophoran affinities. In contrast to popular statements about “living fossils”, the extant Tryblidiida (Neopilinoidea) are regarded as a considerably modified and specialized early conchiferan branch.

Vema levinae Waren, sp. n. is described from a submarine volcano off western Mexico. The type species of Rokopella and Veleropilina are redescribed, the usage of the names is discussed and Rokopella and Veleropilina are recognized as valid genera in Neopilinidae. Rokopella euglypta(Dautzenberg & Fischer, 1897) is redescribed from shells and a single live specimen taken from seamounts south of the Azores, from a depth of 1200–1600 m. Tectura reticulata Seguenza, 1876 (Gastropoda, ‘Acmaeidae’, southern Italy, Upper Pliocene/Lower Pleistocene) is considered to have been based on the monoplacophoran species previously known as Neopilina zografi from the Mediterranean, and is classified in the genus Veleropilina. Veleropilina zografi (Dautzenberg & Fischer, 1896) is redescribed based on shells from several seamounts south of the Azores. It is considered distinct from Rokopella euglypta and classified in the genus Veleropilina. An undescribed species of Veleropilina from a seamount off southern Baja California is reported, figured and discussed but not formally described.

Neopilina rebainsi Moskalev, Starobogatov & Filatova, 1983 Neopilina (Neopilina) sp. Filatova et al. 1974: 675. Neopilina (Lemchephyala) rebainsi Moskalev, Starobogatov & Filatova 1983: 988, figs 5, 7��� 9. The holotype is known from the following locality: Southeast of the Falkland Islands (56 ��29.0'S, 50 �� 51.1 'W), 4660���5630 m. Neopilina of uncertain taxonomic position �� 18 specimens of Neopilina sp. from the southeastern Pacific, Peru��Chile Trench, 2000���6000 m (Menzies 1963) �� number of specimens unknown; as Neopilina sp. from the southeastern Pacific, Milne Edwards Deep of the Peru��Chile Trench, southeastern Pacific (08�� 52 'S, 80 �� 47 'W), 6146���6313 m (Menzies 1968) �� number of specimens unknown; as Neopilina sp. from the southeastern Pacific, Milne Edwards Deep of the Peru��Chile Trench, southeastern Pacific (08�� 46 'S, 80 �� 44 'W), 3909���3970 m (Menzies 1968) �� number of specimens unknown; as Neopilina sp. from the southeastern Pacific, Milne Edwards Deep of the Peru��Chile Trench, southeastern Pacific (11 �� 30 'S, 79 �� 25 'W), 6146���6354 m (Menzies 1968) �� 1 specimen mentioned as Neopilina (Neopilina) sp. from the northwestern Scotia Ridge, southeast of the Falkland Islands (54 �� 43 '�� 54 �� 45 'S, 55 �� 3 '�� 55 �� 37 'W), 1647���2044 m (Rosewater 1970) �� 1 specimen mentioned as Neopilina sp. from the southeastern Pacific off Chile (23 �� 50 'S, 71 ��06'W), 4600 m (Moskalev et al. 1983) Genus Rokopella Starobogatov & Moskalev, 1987 Type species: Neopilina oligotropha Rokop, 1972, by original designation., Published as part of Schwabe, Enrico, 2008, A summary of reports of abyssal and hadal Monoplacophora and Polyplacophora (Mollusca) *, pp. 205-222 in Zootaxa 1866 on page 208, DOI: 10.5281/zenodo.183815, {"references":["Moskalev, L. I., Starobogatov, Y. I. & Filatova, Z. A. (1983) New data on the abyssal Monoplacophora from the Pacific and South Atlantic Oceans. Zoologiceskij Zurnal, 62 (7), 981 - 996.","Filatova, Z. A., Vinogradova, N. G. & Moskalev, L. I. (1974) New finding of the ancient primitive mollusc Neopilina in the Atlantic part of the Antarctica. Nature, 249, 675.","Menzies, R. J. (1963) General results of Biological Investigations on the deep-sea fauna made on the U. S. N. S. Elatnin (U. S. A. R. P.) during cruise 3 between Panama and Valparaiso, Chile in 1962. Internationale Revue der gesamten Hydrobiologie, 48 (2), 185 - 200.","Menzies, R. J. (1968) New species of Neopilina of the Cambro-Devonian class Monoplacophora from the Milne- Edwards deep of the Peru-Chile Trench, R / V Anton Bruun. Marine Biological Association of India, Proceedings of the Symposium on Mollusca, 1, 1 - 9.","Rosewater, J. (1970) Monoplacophora in the South Atlantic Ocean. Science, 167, 1485 - 1486.","Rokop, F. J. (1972) A new species of Monoplacophoran from the Abyssal North Pacific. The Veliger, 15 (2), 91 - 95."]}

Neopilina bruuni Menzies, 1968 Neopilina (Neopilina) bruuni Menzies 1968: 2, figs 1 c, 4 A���E, 5. Although the holotype was originally described from the Anton Bruun Cruise 11, Station 197 (from the southeastern Pacific, Milne Edwards Deep of the Peru��Chile Trench: 11 �� 30 'S, 79 �� 25 'W, 6146���6354 m), a few pages later (p. 8) the author listed the species being from Station 179: Milne Edwards Deep of the Peru��Chile Trench, Southeast Pacific (08�� 54 'S, 80 �� 41 'W). It is most likely that this latter station is correct and the original ��� 197 ��� numbers were mixed up, as other monoplacophorans were reported from Station 197 (Vema ewingi (Clarke & Menzies, 1959; Neopilina sp.), and no other monoplacophoran was listed under this station (which indicates that the species was not mixed). It seems necessary to restrict the type locality to Station 179. The holotype was thus found at a depth of 4823���4925 m as cited without comments in recent works (e.g., War��n & Hain 1992, Counts 2006, Haszprunar 2008)., Published as part of Schwabe, Enrico, 2008, A summary of reports of abyssal and hadal Monoplacophora and Polyplacophora (Mollusca) *, pp. 205-222 in Zootaxa 1866 on page 207, DOI: 10.5281/zenodo.183815, {"references":["Menzies, R. J. (1968) New species of Neopilina of the Cambro-Devonian class Monoplacophora from the Milne- Edwards deep of the Peru-Chile Trench, R / V Anton Bruun. Marine Biological Association of India, Proceedings of the Symposium on Mollusca, 1, 1 - 9.","Clarke, A. H. & Menzies, R. J. (1959) Neopilina (Vema) ewingi, a second living species of the Paleozoic class Monoplacophora. Science, 129, 1026 - 1027.","Waren, A. & Hain, S. (1992) Laevipilina antarctica and Micropilina arntzi, two new monoplacophorans from the Antarctic. The Veliger, 35 (3), 165 - 176.","Counts (III.), C. L. (2006) Chapter 17: Monoplacophora. pp. 211 - 216. In: Sturm, C. F., Pearce, T. A. & Valdes, A. (eds) The Mollusks: A Guide to Their Study, Collection, and Preservation. Universal Publishers, Inc., Boca Raton, Florida, i - xii, 445 pp.","Haszprunar, G. (2008) Monoplacophora (Tryblidia). pp. 97 - 104. In: Ponder, W. F. & Lindberg, D. R. (eds) Phylogeny and Evolution of the Mollusca, University of California Press, Berkeley, Los Angeles, London, i - xii, 1 - 469."]}

Neopilina galatheae Lemche, 1957 (Fig. 1 A) Neopilina galatheae Lemche 1957: 414, figs 1���4. Due to the presence of 10 specimens from the type locality: East Pacific, off Costa Rica (09�� 23 'N, 89 �� 32 'W), 3590 m, the first record of a living representative of the monoplacophora was not only a sensation but also led to numerous detailed studies of the morphology and anatomy of this representative of an ancient lineage. Later the species was recollected in abyssal depths from the following localities: �� specimen number unknown; 3000 km further north of the tip of the southern end of Baja California, 2780���2810 m [it remains unclear whether the author refers to N. galatheae or only to Neopilina sp.] (Wolff 1961) �� 3 specimens from Mexico, Baja California, off Cape San Lucas (22 �� 32.5 'N, 109 �� 40.8 'W), 2781���2809 m (Parker 1961) �� 1 specimen from the East Pacific, off Costa Rica (10 ��07'N, 89 �� 50 'W), 3718 m (Menzies & Layton 1962) �� 1 specimen (mentioned as ��� Neopilina aff. Galatheae ���) from the southeastern Pacific, off Chile (05�� 51.7 'S, 81 �� 48.8 'W), 5300���5320 m (Moskalev 1977)., Published as part of Schwabe, Enrico, 2008, A summary of reports of abyssal and hadal Monoplacophora and Polyplacophora (Mollusca) *, pp. 205-222 in Zootaxa 1866 on page 208, DOI: 10.5281/zenodo.183815, {"references":["Lemche, H. (1957) A new living deep-sea mollusc of the Cambro-Devonian class Monoplacophora. Nature, 179, 413 - 416.","Wolff, T. (1961) Animal life from a single abyssal trawling. Galathea 2 Report, 5, 129 - 162, pl. 9.","Parker, R. H. (1961) Speculations on the origin of the invertebrate faunas of the lower continental slope. Deep Sea Research, 8 (3 - 4), 286 - 293.","Menzies, R. J. & Layton, W. (1962) A new species of Monoplacophoran Mollusc, Neopilina (Neopilina) veleronis from the slope of the Cedros Trench, Mexico. Annals and Magazine of Natural History, 5 (13), 401 - 406, pls 7 - 10.","Moskalev, L. I. (1977) Towards a revision of molluscs Lepetidae (Gastropoda, Prosobranchia) of the world ocean. Works of the P. P. Shirshov Institute of Oceanology, Academy of Sciences U. S. S. R., 108, 52 - 78."]}

Neopilina rebainsi Moskalev, Starobogatov & Filatova, 1983 Neopilina (Neopilina) sp. Filatova et al. 1974: 675. Neopilina (Lemchephyala) rebainsi Moskalev, Starobogatov & Filatova 1983: 988, figs 5, 7– 9. The holotype is known from the following locality: Southeast of the Falkland Islands (56 °29.0'S, 50 ° 51.1 'W), 4660–5630 m. Neopilina of uncertain taxonomic position ­ 18 specimens of Neopilina sp. from the southeastern Pacific, Peru­Chile Trench, 2000–6000 m (Menzies 1963) ­ number of specimens unknown; as Neopilina sp. from the southeastern Pacific, Milne Edwards Deep of the Peru­Chile Trench, southeastern Pacific (08° 52 'S, 80 ° 47 'W), 6146–6313 m (Menzies 1968) ­ number of specimens unknown; as Neopilina sp. from the southeastern Pacific, Milne Edwards Deep of the Peru­Chile Trench, southeastern Pacific (08° 46 'S, 80 ° 44 'W), 3909–3970 m (Menzies 1968) ­ number of specimens unknown; as Neopilina sp. from the southeastern Pacific, Milne Edwards Deep of the Peru­Chile Trench, southeastern Pacific (11 ° 30 'S, 79 ° 25 'W), 6146–6354 m (Menzies 1968) ­ 1 specimen mentioned as Neopilina (Neopilina) sp. from the northwestern Scotia Ridge, southeast of the Falkland Islands (54 ° 43 '­ 54 ° 45 'S, 55 ° 3 '­ 55 ° 37 'W), 1647–2044 m (Rosewater 1970) ­ 1 specimen mentioned as Neopilina sp. from the southeastern Pacific off Chile (23 ° 50 'S, 71 °06'W), 4600 m (Moskalev et al. 1983) Genus Rokopella Starobogatov & Moskalev, 1987 Type species: Neopilina oligotropha Rokop, 1972, by original designation.

Due to their non-segmented coelom the molluscs occupy a position somewhat away from the centre, or at the margin, of coelomate radiation (Chap. 2). Spiral segmentation of the egg is common to molluscs, annelids, and certain platyhelminthes (Polyclads, Turbellaria, Nemertids), and the trochophore larva of the annelids is also developed in the gastropods, scaphopods and many bivalves. However, the paired organs (muscles) known from fossil monoplacophorans or from the extant genus Neopilina (branchia, nephridia) are not vestiges of a primitive segmented annelid ancestor. Rather, they are independent acquisitions developed from a seriated protocoelomate, a common ancestor to the coelomates, and generally preserved by primitive forms of the phylum. Recent comparative results from molecular biology on the nucleotide sequence of ribosomial RNA again suggest closer ties between the annelids and the molluscs with a common source close to the arthropods.

All discussions hitherto on the origin of the coelom have postulated a reduction within the molluscs; moreover, the recent discoveries of Tryblidiacea (Neopilina) have led persistently again to the opinion that the molluscs should have developed from metamerically segmented ancestors. But, as there are neither ontogenetical nor anatomical reasons, the reduction-theory cannot be upheld. The whole organization of the Mollusca (including locomotion, muscular system, nlesenchyme, digestive apparatus, nervous system, larval features, etc.) proves on the other hand that this evolutionary stem must have developed from turbellariomorphic ancestors. The continuity in the locomotion of the molluscs brought from these flatworms guarantees that they did not need a hydrostatical coelom for locomotion (as in other coelomates) and that, therefore, such a coelom has never existed. According to the 'Functional Coelom Theory' the coelom (like every organ) is provided with a special function, and ontogeny as well as the morphological structure of the molluscs refers to the statement that the molluscan coelom has developed as a purely protective pericardium; comparable situations within other animal groups confirm this opinion. The enclosure of the germ cells in the rostral part of the coelom has led to a gonopericardium with double function, and further to a separation in the working organ: pericardium (with coelomoducts) and gonocoel (witl gonoducts). The coelomic cavity of the molluscs therefore proves its own development, which is homologous with that of coelomates by way of the cleavage-cell 4d and the derived mesodermal bands. The gonopericardial room itself, however, cannot be considered as a homolog of the secondary body cavity, so that there is a functionally effected diphyletic development of the coelom within molluscs and other coelomates.

of the occurrence of neurosecretory sub? stances in axons was also made by Scharrer on Pleurobranchaea. It is now generally recognized that neurosecretory substances are formed in the cell body of a neuron and are carried by axoplasmic flow to the terminals for storage and release. In a series of papers, Gabe (1949, 1951, 1953a and b, 1954, 1955) reported finding neurosecretory cells in a wide variety of molluscs, including a scaphopod, some 25 species of prosobranchs, 35 species of opis? thobranchs, and representatives of four orders of lamellibranchs. No one, to my knowledge, has yet found neurosecretory cells in amphineura or cephalopods, and, thus far, a properly fixed specimen of the monoplacophoran, Neopilina, has not fallen into the hands of a neurosecretion enthusiast.

Analysis of a recent compilation of information on marine mollusks living at 1000 fm and deeper has led to several generalizations. The most important are as follows: 1. 1. The composition of the abyssal mollusk fauna differs from that of typical shallow-water mollusk faunae in several respects. Especially noteworthy, both in terms of species and of specimens, is the preponderance of protobranch bivalves in the deep sea. To a lesser extent septibranch bivalves, archaeogastropods and scaphopods are also relatively more abundant there. Differences at the family and genus levels also exist. 2. 2. On the basis of their probable food source, the 1152 known species of abyssal mollusks may be grouped into four categories as follows: 28 per cent feed on plant detritus deposited on the bottom, 51 per cent feed on living bottom animals or animal detritus deposited on the bottom, 16 per cent feed on organic material in suspension, and 5 per cent are parasites. A table of deep-sea families and genera showing number of species in each taxon, food relationships and geologic age is presented. 3. 3. Except for several of the cephalopods and one bivalve (Cyclopecten vitreus (Gmelin)), the abyssal species each appear to be restricted to a small number of ocean basins. In the North Atlantic Ocean the distribution of abyssal species parallels that of shallow water species. 4. 4. A substantial number of abyssal mollusks, particularly bivalves and scaphopods, belong to families with a continuous Paleozoic to Recent fossil record. A smaller but still significant number belong to ancient genera also. However, all abyssal families and genera (except Tryblidiidae and its genus Neopilina) are also represented in shallower depths and the distribution of abyssal mollusks in general is not Tethyan. It is therefore concluded that, at the family and genus level, the first members of the present abyssal mollusk fauna to invade the deep sea probably did so in the relatively recent geologic past.

1. The discovery and description of Neopilina has reopened discussion of possible metameric segmentation in the primitive molluscs. This has involved reconsideration of the multiplied organ systems...

Originally known as fossils from the Cambrian to the Devonian, the finding of a living monoplacophoran mollusc in 1952 was one of the great zoological discoveries of the twentieth century. Now, over 35 living species have been documented from deep-sea locations around the world, mainly from samples collected with trawls. Encountering these animals is extremely rare, and in situ observations are scant. Here, we report two new sightings and ecological data for a probable undescribed species of Neopilina including the first ever high-definition close-up video of these monoplacophorans in their natural environment, obtained while exploring seamount environments in American Samoa. Extensive trackways, similar to those associated with the monoplacophoran siting, may be evidence of a larger population at both seamounts. Living monoplacophorans are important to understanding the recent evolution of deep-sea fauna, yet their habitat, on polymetallic nodules and ferromanganese crusts, is under rapidly increasing pressure for deep-sea mineral extraction.

Living pleurotomariids or slit shells provide a rare glimpse at the biology of remnants of a primitive and predominantly Paleozoic group of gastropods. Discovery of the first living pleurotomariid (Fischer and Bernardi 1856) generated considerable scientific excitement, in precisely the same pattern that later attended the discovery of Neopilina galatheae (Lemche 1957).

The living fossil mollusc examples used here represent three different phylogenetic patterns. The neopilinid monoplacophorans have a disjunct time pattern that separates the living species from the Cambro-Devonian tryblidiid (limpet) monoplacophorans—a gap just short of 430 million years—with the extinction of the last tryblidiid Archaeophiala in the Lower Devonian. The Silurian Pilina unguis (Lindstrom 1880) from the middle Silurian of Gotland is nearly identical (except for shell thickness) to Vema (Vema) ewingi Clarke and Menzies 1959 (Fig. 1).

THE discovery of the living representative of the Monoplacophora, of which a preliminary account by Dr. H. Lemche was published in Nature of February 23, p. 413, is a zoological event of the first order. To a malacologist, at any rate, these dredge hauls off the west coast of Mexico which secured no less than ten specimens with three extra shells of Neopilina galatheae in themselves alone more than justify the voyage of the Galathea around the world.

ON February 22, 1967, R.R.S. Discovery, of the National Institute of Oceanography, dredged a single specimen of the monoplacophoran mollusc Neopilina in the Gulf of Aden. This specimen (Figs. 1–3) represents the first record of the genus beyond the deeps of the eastern Pacific. First collected in 1952 off Costa Rica, and reported by Lemche1, Neopilina is representative of a group previously considered extinct since Devonian times. Up to 1960 it had also been found off northern Peru and Baja California, but no further reports have since been noted and the Discovery record is an indication of much wider distribution than could previously be contemplated.

THE mollusc Neopilina (Monoplacophora) was first found 20 yr ago in the Peru-Chile Trench of the Pacific Ocean1. Neopilina has since been found in other places2–4 including various areas of the Pacific, the northern Indian Ocean and the Atlantic part of the Antarctic. So far, no Neopilina has been encountered in the Atlantic Ocean proper, though it probably occurs there.

Molluscs had a common origin with the annelids, as shown by remarkable ontogenetic similarities. Their common ancestors were non-segmented (non-eumetameric), acoelomate animals. Molluscs developed from the common stock through incorporation of the distinguishing molluscan characters such as the shell, mantle, mantle cavity, radula and ctenidium and annelids by the adoption of coelomic segmentation and of changes accompainying it. The assertion that molluscs hand ancestors with coelomic segmentation is contradicted by ontogenetic and anatomical facts as well as by theoretical considerations. The common molluscan-annelid stock most likely originated from ancestral flatworms; this is indicated by the developmental, and to a lesser extent, structural similarities between the flatworms, molluscs and annelids, and by the lower level of organization of the flatworms. The coelom is a phylogenetically new structure in the molluscs and annelids, and was acquired independently in the two phyla. Coelomic segmentation also is a phylogenetically new acquisition of the annelids; it came about through developmental changes affecting the growth of the mesoderm bands. These views are the corollaries of ontogenetic considerations. IA widely held hypothesis concerning the origin of molluscs is the so-called annelid theory. According to Hyman (1951:4), the "annelid theory" states that ". . . annelids, arthropods, and chordates are closely related and [that] lower bilateral groups may have arisen from annelids by degeneration." In the present paper the term is restricted, referring to the theory that annelids gave rise to molluscs. Early proponents of this theory (Pelseneer, 1899; Heider, 1914; S6derstr6m, 1925; Naef, 1926) believed that the serial repetition of' certain organs in some molluscs represented vestigial segmentation, and claimed on this basis that molluscs descended from the segmented worms, annelids. They also believed that the farreaching similarities in cleavage and early development were further indications of this relationship. More recent investigators added other viewpoints to these arguments. Thus, Garstang (1928) theorized that molluscs evolved from the trochophore larvae of the annelids by neoteny. Johansson (1952) aimed at giving a functional explanation to the annelid theory, when he proposed that the molluscs had lost the segmentation of their annelid ancestors in turning to living on hard, rocky surfaces of the intertidal zone, and assuming a creeping, crawling mode of locomotion. And finally, Lemche (1957) reported the discovery of a "living fossil," a primitive, segmented mollusc, Neopilina galatheae Lemche, 1957. Soon two more species of Neopilina were found, N. ewingi Clarke and Menzies, 1959, and N. veleronis Menzies and Layton, 1963. These discoveries were accepted by many as evidence for the segmented origin of molluscs (Lemche, 1959a, 1959b, 1960; Lemche and Wingstrand, 1959b; Portman, 1960; Fretter and Graham, 1962). Lemche went so far as to postulate that molluscs are more closely related to the arthropods than to the annelids, and that the latter arose independently of the former two groups. Fretter and Graham supported this argument by claiming that the coelom is primarily small in the arthropods as well as in the molluscs. Opponents of the annelid theory have repeatedly pointed out the weaknesses of it. Thus, Nierstrasz (1922), Hammersten and Runnstrom (1925), Ivanov (1928, 1944), Beklemishev (1958a, 1958b), Boettger (1959), Steinbock (1962) and Hunter and Brown (1965) argued that molluscs cannot be considered as annelids with reduced segmentation, because of fundamental anatomical and developmental differences in

In December 1958 the Lamont Geological Observatory research vessel "Vema" dredged four specimens of Monoplacophora from the Peru-Chile Trench off northern Peru. This is the second discovery of living representatives of this class of Mollusca which was thought, until 1957, to have become extinct in the Devonian. The specimens are considered to represent a new subgenus and species: Neopilina (Vema) ewingi , and the discovery suggests that more relict types may exist alive in the deep sea off Central and South America.