120 HELICID^. 



depressed at centre and perforated by a very small um- 

 bilicus. Aperture rounded, forming two-thirds of a 

 circle ; lip white, slightly reflected above, more so 

 below, until at the umbilicus it is quite revolute and 

 mostly covers the opening. Within, flesh color. 



Diameter seven-eighths of an inch ; axis three-fourths 

 of an inch. 



Geogeaphical Distribution. Mr. Lea's specimens 

 were brought from California. Others were obtained by 

 the Explormg Expedition along the Sacramento River. 



Remarks. The general aspect of this species in 

 form and coloration is much like that of ^. arhustorum. 

 The shell is thinner, somewhat more conical, and the 

 aperture larger, with the lip less reflected. It belongs 

 to the same group with S. tudiculata, and has the same 

 general marking ; but it is smaller and more elevated. 

 The coloration vari^ in being more or less clear brown 

 or flecked with ash color. There is also considerable 

 variation in solidity. One specimen deviates so much 

 in these respects and others, that there would be no 

 hesitation in regarding it as a distinct species, were it 

 seen unaccompanied by others. It is quite solid, gray- 

 ish, with a band scarcely perceptible. The strias of 

 growth crowded and beautifully decussated by revolv- 

 ing impressed lines which deviate as they pass over 

 the larger longitudinal ridges. The peristome is much 

 thickened within, so as greatly to contract the aperture. 

 It is represented by the middle figure of Plate VI. 



