Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.

Twenty six species of Scaphopoda, included in 12 genera and five families were identified. Within these, Fustiaria stenoschiza (Pilsbry & Sharp, 1897), Gadila pocula n.comb. (Dall, 1889); G. simpsoni n.comb. (Henderson, 1920) and G. pandionis (Verril & Smith in Verril, 1880) are recorded for the first time for Brazil and two new species of the genus Cadulus are here described. Besides that, six species previously recorded from north and northeast Brazil have their geographical range expanded southward: Antalis circumcincta (Watson, 1879), Episiphon didymum (Watson, 1879), Ep. sowerbyi (Guilding, 1834), Entalina platamodes (Watson, 1879), Gadila dominguensis (Orbigny, 1853) and Compressidens pressum (Pilsbry & Sharp, 1897). In the other hand, Paradentalium infractum n.comb. (Odhner, 1931) has its geographical distribution extended northward to the state of Maranhão (02ºS). Gadila acus (Dall, 1889) is proposed as junior synonym of G. dominguensis (Orbigny, 1853).

The temperate zone of the southwestern Atlantic Ocean (23-42°S), which includes the Patagonian Shelf Large Marine Ecosystem and the Subtropical Convergence Zone, is one of the most productive areas of the Southern Hemisphere. Key features of this region are a wide continental shelf, the convergence of cold and warm currents, and continental freshwater input of the La Plata River. The Uruguayan marine and estuarine waters are at the core of this zone. The marine and estuarine bivalve fauna of Uruguay has received good attention since the publication of the Voyage of Alcide d'Orbigny (1834)(1835)(1836)(1837)(1838)(1839)(1840)(1841)(1842)(1843)(1844)(1845)(1846). Here we provide an overview of taxonomic, faunistic and b iogeographic issues, identifying knowledge gaps and highlighting priorities for future research. The main threats for that fauna are discussed, with emphasis on species of current or potential socioeconomic interest. Of the 231 species reported from the area, only four species are strictly estuarine: Erodona mactroides Bosc, 1801, Tagelus plebeius (Lightfoot, 1786), Brachidontes darwinianus (d'Orbigny, 1842) and Mytella charruana (d'Orbigny, 1842). All of these have large biomasses, as is also the case for the marine eurihaline Mactra isabelleana d'Orbigny, 1846. A total of 112 deep-sea species (i.e., living deeper than 200 m) are recorded for the region, including almost every known group occurring elsewhere in deep-sea basins, with the exception of sunken wood associated species. Of these, 38 have been recorded only from the Argentine Basin. Some new records are preliminarily reported and discussed, including

Gadila elongata comb. nov. was described in 1920 from the northern Gulf of Mexico. Until recently, it was only known from the type locality. Herein we present the first record of G. elongata from Brazil (Northeast coast, Ceará state, collected at 177 m) and a morphometrics analysis of the Brazilian species of Gadila. A multivariate Discriminant Function Analysis, based on nine shell morphometric variables (length, maximum diameter, length to maximum diameter ratio, distance of point of maximum diameter from anterior aperture, maximum curvature, anterior aperture height to anterior aperture width ratio, apical aperture height, apical aperture width and apical aperture height to apical aperture width ratio) enabled the distinction between all species studied. Comparisons of shell morphometrics show that length and length to maximum diameter ratio are the most important variables in the differentiation of Gadila species

The genus Bathycadulus Scarabino, 1995 was described on the basis of a bathyal species (Bathycadulus fabrizioi Scarabino, 1995) collected from the southern Indian and western Pacific waters. Here we describe three new species, and conduct a morphometric analysis of shells of the four species. Those findings confirming the rather large bathyal and abyssal geographic distribution of the genus.

A new genus and 13 new species of Scaphopoda (ten Dentaliida and three Gadilida) are described from the tropical Pacifi c Ocean in the Coral Sea, Solomon Islands, Vanuatu, Fiji, Wallis Island and Tonga. Th e new genus is named Boissevainia n. gen. and the new species are Paradentalium choneides n. sp., P. danielleae n. sp., Fustiaria electra n. sp., F. diaphana n. sp., Gadilina lauensis n. sp., Episiphon joanae n. sp., E. wallisi n. sp., E. indefensum n. sp., E. kantori n. sp., E. lacteum n. sp. (Dentaliida); Bathoxiphus kathieae n. sp., Annulipusellum aenigmaticum n. sp. and Boissevainia mossiae n. gen., n. sp. (Gadilida). Th e new taxa not only highlight the diversity of the class in the tropical Pacifi c Ocean, but also indicate the presence of morphologies not yet recorded for the region or described for the class. RESUMÉ Un nouveau genre et treize nouvelles espèces de Scaphopoda (Mollusca) de l'océan Pacifi que tropical. Un nouveau genre et 13 nouvelles espèces de Scaphopoda (dix Dentaliida et trois Gadilida) sont décrits pour l'océan Pacifi que tropical, Îles Salomon, Vanuatu, Fidji, Île Wallis et Tonga. Le nouveau genre est nommé Boissevainia n. gen. et les nouvelles espèces sont : Paradentalium choneides n. sp., P. danielleae n. sp., Fustiaria electra n. sp., F. diaphana n. sp., Gadilina lauensis n. sp., Episiphon joanae n. sp., E. wallisi n. sp., E. indefensum n. sp., E. kantori n. sp., E. lacteum n. sp., (Dentaliida) ; Bathoxiphus kathieae n. sp., Annulipusellum aenigmaticum n. sp. et Boissevainia mossiae n. gen., n. sp. (Gadilida). Non seulement les nouveaux taxons mettent en valeur la diversité de la classe dans l'océan Pacifi que tropical, mais ils indiquent également la présence de morphologies non encore décrites pour cette région ou pour la classe.

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