PLANORBIS. 



ns 



Planorhis traskii, Lea. — Shell large, dark horn- 

 colored, subcylindraceoys, minutely, regularly 

 and closely striated, deeply and broadly iimbili- 

 cated above ; more excavated below ; whirls five, 

 acutely carinated at the periphery above, ob- 

 tusely carinated below ; aperture ear-shaped. 



Kern Lake, Tulan Co., California: Dr. Trask. 

 (Lea.) 



Fig. 188. 



Plnnorbis traskii. 



Planorljis tenuis, Phil. — Shell large, thin, rather shining, very 

 delicately striate, pale horn or smoke-colored ; concave on each side, um- 

 bilicated above, deeply excavated below ; whirls 

 swollen, rounded, above narrow, subcarinated Fig. 189. 



below and rapidly increasing ; aperture sinuous, 

 sub-auriculate. (Z).) 



Shell large, very thin, densely and sharply 

 grooved, transparent, pale horn-color, yellowish 

 or sometimes reddish-brown, not very highly 

 polished ; five rapidly increasing involute whirls, 

 rounded and ventricose above, below narrow and 

 grooved near the suture ; carina usually more pro- 

 minent on the inner whirls, being often obsolete on 

 the body whirl. Upper side umbilicated, so that the 

 deeply depressed first whirl is covered by the rest ; 

 the under side, on the other hand, is almost funnel- 

 shaped, yet flat in the middle. The auricular 

 aperture is somewhat raised above ; the parietal 

 wall has a very delicate callus. Breadth 7-9 lines, 

 height 3|-5 lines. 



Common among graves near Mexico, with Lim- pjanorbis tenuis, 



naetis siibulatus, Dkr. : Schiede and David. 



Resembles Plan, peruvianus, Brod., which has a smaller, thicker shell, 

 and very thick and broad lip. (Kiister.) 



Planorhis tenuis, Philippi, Conch, tab. I, 17, IG, f. 23-25. 



Chemn. ed. 2, 45, pi. ix, f. 14-19. 

 Planorhis mexicanus, Ziegler in litt. 



-KusTEK m 



