New Hydrobiid Snails (mollusca: Gastropoda: Prosobranchia: Truncatelloidea) from North America

— The following new species of Cochliopinae (Prosobranchia: Hydrobiidae) are described: Aroapyrgus polius from Mexico; Cochliopa perforata from Costa Rica; Heleobops clytus from the Dominican Republic; H. torquatus from Jamaica; Lithococcus aletes from Costa Rica; and Littoridina microcona from Costa Rica. In addition, the following new genera and species are described: Mesobia pristina from Honduras; and Texapyrgus longleyi from the United States (Texas). The following new aquatic snails are described as preliminary to a generic review of the Cochliopinae Try on, 1866 (Hershler & Thompson 1991). These novelties represent major geographic range extensions for their respective genera, or they will be used as the basis for anatomical descriptions of taxonomic importance. The new taxa are differentiated from either related genera or other congeners. While provision of anatomical data largely is limited to descriptions of the new genera, it should be noted that generic placement of ' The group of predominantly New World genera of Hydrobiidae united by possession of a sperm tube in the female genital tract (partly or completely separated from the glandular oviduct) and with male penis often having apocrine glands or papillae has been accorded subfamilial status by most recent workers and usually is referred to as the Littoridininae. However, the oldest available and therefore the valid name for this group is Cochliopinae Tryon, 1866. Authorship of Littoridininae has been attributed to Gray, 1857 (without complete literature citation) by several workers (Parodiz 1969:214, Golikov & Starobogatov 1975:211,Ioganzen & Starobogatov 1982:1144, Ponder & Waren 1988:297), but in Gray's works invariably he included the type species of Littoridina in the genus Littorina (Littorinidae) and we have found no evidence that he ever created a family-group name based on this hydrobiid. The earliest such name based on Littoridina is Littoridineae Thiele, 1928. the other new species was confirmed by study of soft parts when available. Material studied is housed in the National Museum of Natural History (USNM) and Florida Museum of Natural History (UF). Shells were measured using WILD M-5 and M-7 dissecting microscopes equipped with ocular micrometers. Measurements are standard and have been converted to mm. Abbreviations are as follows: SH = shell height; SW = shell width; ApH = aperture height; ApW = aperture width; HBW = height of body whorl; WBW = width of body whorl; WH = whorls. The diameter of the apical shell whorl was measured perpendicular to the initial suture. Family Hydrobiidae Troschel, 1857 Subfamily Cochliopinae Tryon, 1866 Aroapyrgus polius, new species Fig. 1, Table 1 Description. —Shell medium-sized for the subfamily Cochliopinae, about 2.9-3.7 mm tall in adults; without obvious sexual dimorphism. Elongate-ovate with an obtuse apex. Width/height 52-63%; thin and transparent; smooth; teleoconch sculpture of very fine collabral striations. Periostracum gray. About 4.6-5.4 whorls in adult specimens; whorls inflated with a deeply impressed suture. Apical whorl low protruding; about 670 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON Fig. 1. Aroapyrgus polius, new species, holotype, UF 175028. Shell height, 3.7 mm. 0.23 mm in diameter. Umbilicus perforate; slightly obstructed by columellar lip. Aperture 37-41% of shell height; broadly ovate; width/height 80-85%; with an obtuse angle at the posterior corner. Aperture prosocline, inclined at 21-26° to coiling axis. Peristome complete across parietal margin of aperture, attached to previous whorl. Outer lip simple and thin; neither reflected nor thickened internally. Outer lip straight in lateral profile. Operculum thin, transparent, corneous; paucispiral, consisting of three rapidly expanding whorls; nucleus eccentric. Type locality.—A small spring-fed pool 3.5 km northeast of Tamazulapan del Progreso, Oaxaca, Mexico; 2100 m elevation. Holotype: UF 175028; collected 19 Oct 1970 by Fred G. Thompson. Paratypes: UF Table 1.—Shell parameters for Aroapyrgus polius. X = mean, SD = standard deviation. sit sw ApH ApW Wh sw