AMERICAN SPECIES OP VERTIGO. 139 



V. modesta group that a distinction may be impracticable; 

 yet the want of any trace of a crest behind the lip may serve 

 to distinguish the present series from most of the modesta 

 group. Moreover, the two groups differ so widely in zonal 

 distribution that a different ancestry is suggested: the cali- 

 fornica group inhabits low levels, while the modesta group is 

 restricted to the colder Canadian and Transition zones, at 

 higher elevations in California, descending to low levels only 

 in the north. 



Key to species and subspecies. 



1. Sculpture of rather strong oblique riblets. 2. 

 Surface striate but not distinctly ribbed; about 2.5 mm. 

 long. Four well developed teeth. V. rowelli, no. 30. 



2. Aperture having 4 teeth, at least the columellar, parietal 

 and lower palatal well developed. 3. 

 Aperture having 3 small teeth. Monterey. 



V. c. trinotata, no. 29a. 

 Aperture having 1 tooth, the parietal, or none. 6. 



3. About 2.5 x 1.3 mm. ; parietal lamella not entering deeply. 

 San Francisco. V. californica, no. 29. 

 Shell smaller or narrower; parietal lamella long, entering 

 rather deeply. Monterey southward, and the islands. 4. 



4. Shell 2 to 2.5 mm. long. V. c. elongata, no. 29d. 

 Shell 1.75 to 2 mm. long; whorls short. 5. 



5. Sculpture strongly developed. S. Catalina and S. 

 Clemente. V. c. catalinaria, no. 29e. 

 Sculpture weaker and irregular, Cypress Point. 



V. c. cupressicola, no. 29/. 



6. San Diego southward. V. c. diegoensis, no. 29&. 

 Placer county. V. c. cyclops, no. 29c. 



29. VERTIGO CALIFORNICA (Rowell). PL 9, figs. 1, 2. 



' ' Shell rimate subperf orate, elongate ovate, thin, dark horn 

 colored, with oblique rib-like striae ; apex obtuse ; deep suture ; 

 with 5-6 convex whorls, the last a little compressed at the 

 aperture; aperture oblique, suborbicular, armed with four 

 white denticles: one lamelliform, strongly developed, slightly 



