COCHHOPA. 



73 



Amnicola 

 rowellii. 



Station, fresh water. 



Distribution, California. {Stimpson.) 



Cocliliopa rowellii, Teyon.— Shell depressed, wider than high, 

 consisting of 3^ whirls, which are regularly convex and rapidly enlarging ; 

 spire small, but little elevated, apex acute, sutures well mark- 

 ed ; base convex, except that the region surrounding the um- Fig. 143. 

 bilicus is flattened and inclining towards the axis, its outer 

 boundary, consequently, is marked by an angle ; umbilicus 

 small, but very distinct ; aperture half-ovate, the labrum well 

 rounded, and thin, the labium but slightly rounded, thickened, 

 elevated from the body-whirl, forming an acute angle with the 

 labrum above, and not impinging on the umbilicus. Surface marked with 

 close, regular, minute striae, which become enlarged in the flattened um- 

 bilical region into sharp crowded lines visible without a glass. Color 

 light horn or yellowish, operculum darker. Operculum paucispiral, the 

 lines of accretion very distinct and regular. Length 2.5, diam. maj. 4, 

 min. 3 ; length of apert. 2, breadth 1 J mill. 



Clear Lake, California : Rev. J. Rowell. My cabinet and cab. of Mr. Rowell. 



This species cannot be compared with any hitherto described, being 

 much more depressed, and widely distinct in the form of the umbilical 

 region. It may possibly form a species of the genus Somatogyrus, recently 

 proposed by my friend Mr. Theo. Gill for a small mollusk from Iowa, 

 which I described in the Proceedings of the Academy for Sept. 1862. 

 (TV^on.) 

 ■ Amnicola rowellii, Tkyon, Proc. Phila. Acad. 1863, 147, pi. i, 



f. 8, 9. F^S- 144. 



In addition to tlie fac-simile of one of the original 

 figures of this species given above, Fig. 144 is drawn 

 from No. 9312 of the collection, which was presented 

 by Mr. Tryon. 



GILLIA, Stimpson. 



Lingual dentition of the type : Ehachidian tooth moderately 



long, deeply trilobate below; basal teeth close to the basal 



margin, and projecting beyond it. Intermediate tooth with the 



body subrhomboidal, slightly excavated in the middle. Outer 

 17 



