sixteen to twenty on the body whorl : volutions in contact : 

 body ivhorl with an elevated line below the middle, and on 

 the suiDerior edge of the inferior band : aperture with the 

 margin robust, white, somewhat dilated at the base. 



OBSERVATIONS. 



This species is not uncommon on our southern coast. 

 Its length is about half an inch. A variety occurs, of 

 which the costae are almost obsolete, and another in W'hich 

 each rib, particularly of the body whorl, has an impressed 

 line. The margin of the mouth is greatly thicker than the 

 ribs. What I have called in the above description an ele- 

 vated line, is strictly speaking, the line of junction with 

 tlie basal surface which is a little more elevated than the 

 remaining surface of the volution, making a kind of step, 

 and not in reality a simple elevated line. In my observa- 

 tions on this species, in the Journal above mentioned, I re- 

 marked that it '• very much resembles the clathratulus, 

 Montagu, but the lip is more robust and the basal portion 

 of that part is more dilated," 



REFERENCE TO THE PLATE. 



The lovTcr left figure is- a. front somewhal enlarged view ; the line represents 

 the natural lengtl), and the outline figure iaimcdiately above is a still more cr- 

 largod reproecntation of the body whorl, to show the bands and the elevated 

 lino. 



PLATE XXVII, 



