MOLLUSC A OR UNIVALVES. 241 



neighbouring islands, and they are taken at 

 night and at sunrise, when they are probably 

 feeding. Some naturalists* affirm that the 

 animal can, when attacked by an enemy, dis- 

 embarrass itself of part of its foot, and retire 

 entirely within its shell. The ribs in this genus 

 are evidently the remains of what has been the 

 mouth of the shell at different periods. The 

 H. ventricosa is the most common species of 

 this genus, and perhaps the most beautiful. 



107. Dolium. — Shell large, light, globular; 

 mouth wide and notched, ge- 

 nerally transversely banded, and 

 the right lip in consequence 

 waved ; operculum horny. Ani- 

 mal, head large, having a short 

 proboscis, and two tentacula with 

 eyes in the middle ; foot rather large. — 7 

 species, recent. 



These shells are found, for the most part, in 

 the seas of the Indies, Africa, and South Ame- 

 rica : one species, however, the Dolium galea, 

 is met with in the Mediterranean. They are 



* MM. Quoy and Gaimard, and M. Reynaud, 



