PTEROPODA. 249 



CLASS II. 

 PTEROPODA. 



The Pteropoda, like the Cephalopoda, swim in the ocean, but 

 being deprived of feet, can neither fix themselves to other bodies, 

 nor crawl. Their organs of locomotion consist of fins placed like 

 wings on the two sides of the mouth. But few and small species 

 are known. 



CLIO, Lin. 



Body oblong, membranous, without a mantle; head formed of two round- 

 ed lobes, whence originate small tentacula; two small fleshy lips, and a little 

 tongue on the front of the mouth; the fins covered with a vascular net-work 

 which acts as branchiae. Some authors consider them as possessing eyes. 



Clio borealis, L. This species, which is the most celebrated, is found in 

 astonishing numbers in the arctic seas, furnishing, by its abundance, food for 

 the Whales, although each individual is hardly an inch long. 



CYMBULIA, Peron. 



A cartilaginous or gelatinous envelope resembling a galley, or rather a sabot 

 or wooden shoe, bristling with small points disposed in longitudinal rows. 

 The animal has two large wings composed of a vascular tissue, which are 

 its branchiae and fins; between them, on the open side, is a third and smaller 

 lobe with three points. 



PNEUMODERMON, Cuv. 



The Pneumoderma begin to be a little further removed from the Clios. 

 Their body is oval, without a mantle and without a shell; the branchiae are 

 attached to the surface and composed of little laminae arranged in two or 

 three lines so disposed as to form an H on the part opposite to the head. 



LlMACOA, CUV. 



The body terminates in a spirally convoluted tail, and is lodged in a very 

 thin shell formed by one whorl and a half, umbilicated on one side, and 

 flattened on the other. The animal uses its shell as a boat, and its wings as 

 oars, whenever it wishes to navigate the surface of the deep. 



Clio helicina. Almost as common on the arctic seas as the Clio borealis, 

 and is considered as forming the chief source of food for the Whale. 

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