GYMNOSOMATA. 61 



animal is not yet known, but it is supposed, with proba- 

 bility, by Professor Forbes to be Pteropodous. There is but 

 one species known, dedicated to Thomas Huxley, F.R.S., 

 the philosophic Zootomist attached to the " Rattlesnake." 



Order GYMNOSOMATA. 



Body naked, without any shell. Head distinct. Wings 

 two, or four, at the junction between the head and the body, 

 with a central intermediate lobe or rudimentary foot. Gills 

 exterior. 



In this order there are three families, all without shelly 

 covering. The warmer seas doubtless abound in numerous 

 undiscovered forms ; those already known have a single 

 heart, the sexes are united, and the respiratory organs 

 are external. 



Fam. CLIONID^. 



Animal fusiform. Head with a series of conical pro- 

 minences on each side. Wings two, with a central foot- 

 like appendage between them. 



In this family the conical prominences probably repre- 

 sent tentacular arms in a rudimentary condition ; there are 

 two genera, one, Clione, with the head indistinct and the 

 tentacles defined, and the other, Cliodita, with the head 

 Ilstinct, and the tentacles not apparent. 



c 



Genus CLIONE, Pallas. 



Head indistinct ; tentacles six, conical, three on each 

 side. Tooth of lingual membrane broad, convex behind, 

 slightly two-lobed and denticulated In front ; lateral teeth 

 12-12, simple, arched, rather swollen at the base, the outer 

 gradually diminishing in size. 



