MOLLUSC A. OR UNIVALVES. 275 



possessing one or more fins ; the head can be 

 contracted within the body, and is provided 

 with two tentacula, two eyes, and a retractile 

 proboscis. — 3 species recent. 



There are only three species known of this 

 singular genus. The Carinaria vitrea is so 

 called from its resemblance in substance to 

 glass, and is found in the African seas : it is 

 very rare. The Carinaria fragilis is extremely 

 delicate in its texture, and inhabits the Medi- 

 terranean ; and the Carinaria cymbium, or boat- 

 shaped, which is not larger than a grain of sand, 

 and can only be seen with the assistance of a 

 microscope, is brought from the Eastern Ocean 

 and Mediterranean Sea; it is found on the 

 coast near Nice, and feeds on small Medusa and 

 other gelatinous substances, as also on minute 

 fish, and occasionally the more feeble of its own 

 species. 



The mollusca which form these shells are 

 very transparent, but are possessed of lively 

 and brilliant colours ; they only appear on the 

 surface of the sea during calms. The shells are 

 comparatively small, as they only cover the 

 circulating and respiratory organs ; they were 

 T 2 



