192 HELICID^. 



row lunate, the lip forming about two-thirds of a circle, 

 reflected, white, with a constriction behind it, and armed 

 with two denticles at its inner edge, one near the centre, 

 the other at the middle of the basal portion. The extrem- 

 ities of the lip are connected by a callus across the colu- 

 mella, of an acutely angular form, pointing to the middle 

 of the portion of the lip above the upper denticle, the 

 lower ramus of the angle being longest and largest, and 

 a little concave inwardly. 



Diameter three-eighths of an inch, axis three-twentieths 

 •of an inch. 



Geographical Distribution. Collected by Mr. 

 Bartlett at Corpus Christi, and Galveston, in Texas. 



Remarks. The numerous specimens now in our pos- 

 session render the specific value of this sliell no longer 

 doubtful. In the monograph in the Boston Journal of 

 Natural History, it was regarded as a form of ^. auricu- 

 lata ; and M. Fcrussac (Bulletin Zoiilogique, 2d section, 

 85,) referred it to the next species. In the former, even in 

 the immature stage, all the oral appendages are more 

 lamellar, and are not appressed to the shell ; in the 

 mature state, the development of the lip admits of no 

 mistake. It is larger, thinner, and smoother, both above 

 and below. H. fatigiata is smaller, more discoidal, the 

 teeth on the outer hp are deeper within the throat, and 

 the triangular lamella on the columella is obhquely trun- 

 cated at tip, so as to render it linguiform. H. jmstula 

 is still smaller, and has a very different umbihcus. In 



