94 PTEROTRACIIEIDtE. 



the form of a long, slender, moniliform tube, and in others 

 is furnished with a singular leaf-like appendage. The true 

 homologies of the foot and caudal fin in the Pterotra- 

 cheidoe have been pointed out by Huxley ; the locomotive 

 disk, or mesopodium, of ordinary Gasteropods being repre- 

 sented by the sucker, the anterior lobe, or propodium, by the 

 ventral fin, and the operculigerous lobe, or metapodium, by 

 the pointed tail. 



Genus PTEROTRACHEA, Forskiil. 



Tentacles none; head armed in front with conical pro- 

 cesses; eyes large and conspicuous. Body fusiform, ending 

 behind in a prolonged, keeled, conical tail, which is some- 

 times pinnate; nucleus prominent; gills distinct. Ventral 

 fin, or foot, furnished with a sucker. 



Shell none. 



Syn. Firola, Per on and Lesueur. Hypterus, Itajin. 



Ex. P. hippocampus, Philippi ', pi. GO, fig. 7. 



The species of Pterotrachea are probably very numerous, 

 although not yet made known ; they are found in the seas of 

 temperate and tropical climates, and are often marked with 

 coloured spots. The genus was well figured and described 

 by Forskiil, who established it. 



Species of Pterotrachea. 



Blainvilleana, Lesueur. Keraudrenii, Eyd. 



coronata, Forsk. Lesueurii, Bisso. 



Desmarestina, Lesueur. mutica, Lesueur. 



Edwardsii, Desh. pulmonata, Forsk. 



Frederica, Lesueur. Quoyana, D'Orb. 



hippocampus, Phil. rufa, Quoy. 

 hyalina, Chiaje. 



