SOMATOGYRUS. 



77 



Fig. 150. 



Aranicola 



SoiuatogyritS depressus, Tryox.— Shell orbicular, sub-hyaline ; 

 whirls four, convex, the last large, equalling five-sixths the 

 length of the entire shell ; umbilicus narrow ; aperture senai- 

 circular, labrum appressed within ; suture impressed. Length 

 and breadth four mill. (Fig. mag. 2\ times.) 



Hab. Mississippi River, at Davenport, Iowa : Prof. Sheldon. 

 Coll. Acad. Nat. Sciences, and Smithsonian Institution, Prof. 

 D. S. Sheldon, Geo. W. Tryon, Jr. 



Shell subhy aline, rather solid, orbicular, with the spire 

 depressed, consisting of four whirls ; apex acute, suture pro- 

 foundly impressed. Body whirl very convex, equalling five-sixths the 

 length of the shell, narrowly umbilicate. Aperture semicircular, the inner 

 lip being nearly straight. The only shell which this resembles is Vivipara 

 sub(/lohosa, Say, which differs in being double the size of A. depressa, with 

 a rather more exserted spire, and in having a more concave inner lip. 

 iTri/on.) 



Amnicola depressa, Tryox, Proc. Ac. N. Sc. Phila. 1862, p. 452. 

 Somatogyrus depressus, Gill, Pr. Phil. Ac. 1863, 34 (no descr.). 



Fig. 150 is drawu from Mr. Tryon's original figure. 



Cat. No. 1^0. of Sp. 

 9014 



Locality. 



From wbom received. 



Davenport, la. 



G. W. Trvon. 



Fig. 151. 



Fig. 152. 



Somatogyrus isogomis, S.\t. — Subglobose, horn-color, volutions 

 about four, rounded, obsoletely wrinkled ; spire very short, about one- 

 third the length of the ape^tl^re ; suture pro- 

 foundly impressed, so as to form a shoulder on 

 the whirls ; aperture much dilated, oval, being 

 as obtusely rounded above as at base ; um- 

 bilicus linear, distinct ; operculum obviously 

 spiral. Length under three-tenths of an inch. 

 Inhabits Bear Grass Creek, near Louisville. 

 Not very numerous. It is remarkable by 

 the oval form of the much dilated aperture, and by the deeply indented 

 suture. In old specimens the base is almost acutely angulated. (Sny.) 



Melunia i^ogona, Say, N. H. Diss. II, 227 (1829) ; Descr. 19; Bixxey's 



ed. 144. 

 Amnicola isogona, Lea, Tr. Am. Phil. Soc. IX, 16 (1844) ; Obs. IV, 16. 



— Woodward, Man. pi. ix, f. 23. 

 Paludina isogona, DeKay, N. Y. Moll. 85, pi. vii, f. 133. 

 Paludina pallida, Lea, Trans. Am. Phil. Soc. VI, 22, pi. xxiii, f. 104 



(1839) ; Obs. Ill, 22. 

 ? Paludina fontinalis, Phil:ppi, Conch. II, 5, p. 2, pi. ii, f. 9 (1846).— 



KiJSTER, Chemn. ed. 2, 56, pi. x, f. 27, 2S. 



