THE NATURAL HISTORY SURVEY. 343 



culiar aperture. The spire is a trifle elevated. The S. depressus 

 can be considered only a variety. This species is rather com- 

 mon and widely distributed, being found in both the southern 

 and western regions. 



Subfamily Poraatiopslnae. 



Shell: Elongated, perforated; peristome continuous. 

 Foot with lateral sinuses. Operculum paucispiral, without in- 

 ternal process. Amphibious. (Tryon.) 



GENUS POMATIOPSIS Tryon. 



Shell: Elongated, turreted, smooth, subumbilicated; aper- 

 ture roundly ovate; peristome reflected; operculum corneous. 



Animal: With a broad foot, truncated before, rounded 

 behind; tentacles short, pointed, subulate; rostrum large, round, 

 blunt; verge large, broad, rather flat, coiled one and one half 

 times on itself. Jaw as in Amnicola, but smaller. Radula 

 formula 3-1-3; central tooth rather small, square, but a little 

 broad at the base, where are two denticles, reflected cusp tri- 

 dentate; laterals long and somewhat narrow, the inner lateral, 

 however, being broader than the two outer, reflected cusp den- 

 ticulate. The intermediate lateral is four-dentate, and the 

 outer laterals five-dentate. 



Distribution: Eastern North America. 



KEY TO SPECIES OF POMATIOPSIS. 



A. Shell elongated, acute, whorls six lapidaria 



B. Shell conical, proportionately wider than A, whorls four 



cincinnatiensis 



141. Pomatiopsis cincinnatiensis Anthony, pi. xxvi, figs. 8, 9. 



Paludina cincinnatiensis ANTHONY, Bost. Journ. Nat. Hist., Vol. Ill, 

 pt. 1 and 2, p. 279, pi. iii, fig. 3, 1840. 



Shell: Conrcal, turreted ; color greenish or brownish horn ; 

 surface shining, lines of growth crowded together; apex well 

 rounded, obtuse, nuclear whorls smooth, polished; spire short 

 conic in the male but more elongated in the female; sutures 

 deeply impressed; whorls four, well rounded, somewhat ven- 

 tricose; aperture orbicular; peristome rather thin, continuous, 

 appressed to the body-whorl; last whorl very ventricose in the 

 male but not so much so in the female; base of shell rounded; 

 umbilicus narrow, deep. 

 Length, 4.50; width, 2.30; aperture length, 1.50; width, 1.25 mill. (12478 ) ? 



" 5.00; " 3.50; " " 2.10; " 1.50 " (12478.)c? 



" 4.00; " 2.10; " " 1.50; " 1.25 " (12478.)$ 



