Vitrlnella helicoidea. ^dams. 



V. t. discoidea, alba, opaca vel transluceute, linea sutural! impres- 

 sa, et striis transversis inequalibus insculpta : apice pei'obtusa : spira 

 convexa, vix elovata : anfractibus quatuor, subconvexis ,valde accres- 

 centibus; sutura vix impressa : labio subcrasso : umbilico magno, pro- 

 fundo, carina jiHrali iustructo. 



Discoidal : 



white; opaque and translucent in transverse alternating lines: 



with a single impressed spiral line near the summit of the 

 whorls, and very fine irregular transverse strise: 



apex very obtuse : 



spire slightly and convexly elevated : 



whorls four, moderately convex, rapidly increasing, with a 

 lightly impressed suture ; last whorl regularly rounded, a little 

 compressed beneath. 



aperture not modified by the last whorl : 



labium with a rather thick deposit : 



umbilicus large and deep, with a spiral carina, exhibiting all 

 the whorls. 



Mean divergence about 150'^; length of spire .01 inch ; total 

 length .03 inch ; greatest breadth .075 inch ; least breadth .OG 

 inch. 



