FISSURELLA. 265 



visible in E. crassa ; and the slit is shorter relatively to 

 the size of the shell. 



Genus III. FISSUREL'LA*, Bruguiere. PL VI. f. 4. 



Body senrioval : mantle protruded in front through a hole or 

 slit in the crown of the shell : foot covered with papilla?. 



Shell ovately conical, perforated on the anterior side of the 

 crown : beak spiral in the young only : inside thickened around 

 the terminal perforation. 



This is one of the genera of mollusks which Cuvier 

 illustrated in his celebrated Memoires on their ana- 

 tomv. He considered it to be allied to Haliotis. Al- 

 though the animal in its normal state extends beyond 

 the shell, it can be entirely withdrawn into it, like 

 Vitrina. Woodward has well remarked that its organi- 

 zation has certain homological affinities with that of the 

 Lamellibranchiate bivalves, in the number and position 

 of the gills, as well as in the pallial tube. According to 

 Beudant, it is equally incapable with Capulus of existing 

 in fresh water. The opening in the summit of the shell 

 resembles a keyhole ; in the young it is placed on the 

 anterior side of the beak, which is distinctly spiral at 

 that period of growth. The fry might be mistaken for 

 that of Puncturella, if it had also an internal sheath 

 or process. Fissurella is represented in all seas, scantily 

 in the North Atlantic, but amply in southern latitudes, 

 whence many fine and gaily painted species have been 

 brought by collectors. The number of genera into 

 which this has been divided by Gray and other English 

 conchologists was noticed by Philippi as one of the 

 curiosities of science. 



* Having a small cleft in the shell, 

 VOL. III. X 



