158 



POPULAR CONCHOLOGY. 



an oval, thin, nearly transparent plate. Animal, 

 body creeping, oblong; head with four tentacula, 

 furnished with eyes ; mantle 

 large. — There are 22 recent 

 species. 



These animals resemble large 

 slugs ; they swim easily, but 

 crawl slowly : they are found 

 in the Mediterranean Sea. Darwin, in his 

 Journal*, says it feeds on delicate sea-weeds 

 which grow among the stones in muddy and 

 shallow water ; and that he found in the sto- 

 mach of several, small pebbles as in the gizzards 

 of birds. He also mentions that, when irri- 

 tated, it emits a fine purplish-red fluid, which 

 stains the water for the space of a foot round, 

 and that, besides this means of defence, an 

 acrid secretion, which is spread over its body, 

 causes a sharp stinging sensation. He found it 

 at St. Jago. 



32. Dolabella. — Shell oblong, thick, and 

 slightly spiral on the posterior side, thin and 

 flattened on the other. Animal, oblong, hav- 



* Journal of Researches into the Geology and Natural 

 History of the Countries visited by the Beagle. 



