146 HELICID^. 



base, tliin, of a yellowisli green color, having the surface 

 everywhere ornamented with small, crescent-formed scales 

 of the epidermis, in relief, arranged along the lines of 

 growth, and in quincunx. Whorls five and a half, slightly 

 convex, separated by a deeply impressed suture, and 

 fonning a low, conical spire ; the periphery of the last 

 whorl is slightly angular near its posterior portion. The 

 base is rounded, tending rapidly to a deep, umbilical 

 depression, with a small perforation. Aperture small, 

 crescentic, having a small, acute tooth on the right mar- 

 gin, a transversely oblong one at base, and a prominent, 

 compressed, curved, nearly hoi-izontal one on the colu- 

 mella, thus giving a three-lobed outline to the aperture. 

 Peristome white, slightly reflected, having a very pro- 

 found constriction of the whorl directly behind it. 



Diameter one-fourth of an inch ; axis three-twentieths 

 of an inch. 



Geographical Distribution. The specimen from 

 which this description was drawn was brought by the 

 U. S. Exploring Expedition from the Sacramento River, 

 in California. 



Remarks. Its general form, and its aperture, are 

 very much like H. inflecta, Say, though it is a much 

 smaller shell, and the teeth of the aperture are less 

 developed. Its peculiar surface, resembling a scaly 

 coat of mail, when closely examined, is highly charac- 

 teristic. It is interesting as another example of species 

 from the west of the Rocky Mountain range resembling 

 forms on the eastern side. — [g.J 



