52 AMERICAN JOURNAL 



DIAGNOSES OP NEWLY DISCOVERED GENERA OF 



GASTEROFODS, BELONGING TO THE SUB-FAM. 



HYDROBIINJE, OF THE FAMILY RISSOIDJE. 



BY DR. WILLIAM STIMPSON, 

 COCHLIOPA.* 



Shell depressed-conic ; base concave, carinated ; nmbilicus 

 large and deep ; aperture oblique. 



Operculum thin, corneous, subspiral. 



Rostrum, of moderate size ; tentacles rather long, tapering. 

 Yerge geniculated and bifid, the inner branch being very 

 small, less than one-fourth the size of the outer and arising at 

 the inner ano-Je of the geniculation. 



Lingual dentition of the typical species: — Ehachidian tooth 

 short and broad, armed with two denticles on each side of the 

 base, and eleven denticles at the cusp. Intermedia^te tooth 

 with a long peduncle and square body, having a cavity in 

 the centre; cusp with eight denticles. Lateral teeth with an 

 expansion of the inner side of the shank, separated from the 

 summit by a deep rounded sinus ; inner lateral with eighteen, 

 outer one with twenty-four denticles at the summit. 



Station. — Fresh water. 



Distribution. — California. 



Type, C. RowELLii. 



Amnicola RowelUi Tryon,Proc. A. N. Sciences, Philadelphia, 

 1863, p. 147, pi. i., f. 8, 9.— Clear Lake, California. 



FLUMINICOLA. 



Shell comparatively large, obliquely ovate, thick, smooth, 

 imperforate; spire short, obtuse; aperture ovate, inner lip 

 flattened, callous ; outer lip effuse and projecting anteriorly, so 

 that the peritreme is not in the same plane. 



Operculum corneous, subspiral. 



Foot short, broadly rounded behind. Tentacles tapering. 

 Rostrum large. Verge compressed, with a broad, semicircular, 

 laminiform expansion or wing at the left side. 



Lingual ribbon (of type) with the rhachidian tooth twice as 

 broad as long, and trilobate below ; cusp armed with five den- 

 ticles ; basal denticles, three on each side. Intermediate tooth 



* Ko;)(;x;?, cochlea parva ; iTrn. foramen. 



