NEW GENUS OP MOLLUSKS. 475 



a precarious existence on roots and goats'-flesh. They 

 are not, however, sufficiently versed in geologic lore to 

 understand on what ticklish ground they tread, or that they 

 stand a chance of being one day either burnt or drowned. 



The Mollusk that constructs the shell of Sulla viridis, 

 Rang, would appear to form the type of a new genus, 

 which may be thus characterised. Smaragdinetta : body 

 oval, and somewhat depressed; lateral lobes moderate, 

 reflexed, covering a small portion of the sides of the shell, 

 opened and produced in front, and rounded posteriorly 

 where they are continuous with the foot ; foot moderate, 

 rounded before and behind ; head-disc five-sided, narrow 

 and notched behind, rather broader on each side in front, 

 flattish above, with two small tubercular tentacles in front 

 of the central eyes, which are round, black, sessile, and 

 placed rather wide apart. Shell partly external and 

 naked above, with the body whorl turned inwards, open, 

 and forming a very peculiar, shallow, cup-shaped process, 

 which renders it quite different from other Bullidce. 



The animal of Sulla viridis of Rang, or the Sulla 

 calyculata of Sowerby, is figured in the Voyage of the 

 Astrolabe (t. 26, f. 13.) In that figure are correctly repre- 

 sented the peculiar prolongation of the lateral lobes for- 

 wards, the square-shaped cephalic disc, and the two 

 round sessile eyes ; but in the animals 1 examined there 

 were observed the rudiments of two tentacular processes, 

 situated anterior to the eyes. The head-disc in this genus, 

 as in other Bullida, occasionally assumes various forms 

 according to the will of the animal, being either deeply 

 indented in front with lateral sharp projecting angular 

 processes, or rounded lobes, or very much produced in 



