320 MOLLUSC A. 



CLASS IL 



PTEROPODA(l). 



The Pteropoda, like the Cephalopoda, swim in the oceany 

 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, all of them hermaphrodites. 



Clio, Lin. — Clione, Pall. 



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

 rounded lobes, whence originate small tentacula; two small fleshy 

 lips, and a little tongue on the front of the mouth j the fins covered 

 with avascular net-work which acts as branchiae, the anus and geni- 

 tal orifice under the right one. Some authors consider them as pos- 

 sessing eyes. 



The external envelope is far from being filled with the viscera; the 

 stomach is wide, the intestine short, and the liver voluminous. 



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(2). 



Brugiere has observed a larger and not less abundant species 

 in the Indian Ocean; it is distinguished by its rose colour, emar- 



(1) M. de BlainvUle unites my Pteropoda and my Gcs^erqpoc^a in a single class, 

 which he calls Paracepiialopiioka, of vfc'hich my Pteropoda form a particular order, 

 under the name of Apohobranchiata. This order is divided into two families; the 

 Thecosoma, which are furnished with a shell, and the Gymnosoma which are not. 



(2) The C7to iorm/is of Pallas (Spicil, X, pi. 1, f. 18, 19), the Clio retusa of 

 Fabricius (Faun. Groen., L., 334), and the Clio lamacina oi' Plupa (Ellis, Zooph., 

 pi. 15, f. 9, 1, 10), of which Gmclin makes as many different species, appear to be 

 this same animal. 



