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Cyanocyclas brasiliana (Deshayes, 1854) known only from the original very short description and reported from Pará state was recently rediscovered. This is the first occurrence of a native species of Cyrenidae (formerly Corbiculidae) in the Northeast Region of Brazil. Due to a lack of previous data C. brasiliana was initially confused with Corbicula largillierti (Philippi, 1844), an invasive species of Asian origin, which was introduced in South America in the 1970s and already recorded from the North and Northeast regions of Brazil. Ecological aspects are described. To aid identification, type material was studied.

Leaf litter represents a food source to many organisms that may directly contribute to organic matter decomposition. In addition, the physical presence of these vegetal detritus contributes for the modification of some environmental areas and produce microhabitats that may act as a refuge against predators and desiccation for many animals. The pulmonate gastropod Melampus coffeus (Linnaeus, 1758) (Ellobiidae) is a very common specie in Atlantic Coast mangrove forests and feeds on fallen mangrove leaves. It was hypothesized that the spatial distribution of Melampus coffeus is directly affected by mangrove leaf litter biomass deposition. Thus, this research aimed at evaluating the spatial distribution of these gastropods in relation to the biomass of mangrove leaf litter through a twelve-month period. The study area was established in the middle estuary of Pacoti River, state of Ceará, Brazil where two adjacent zones with different topographic profiles were determined. Samples of Melampus coffeus and leaf litter were collected monthly, throughout a year, from the mangrove ground surface. The results indicated that the presence of twigs in mangrove litter favor the occupation by smaller individuals of M. coffeus, probably because smaller individuals are more susceptible to predator attacks and desiccation than larger ones, and twigs and branches may provide a safe microhabitat.