SPONGIOBRANCniA. 63 



In this family the genera are distinguished principally 

 by the gills, which in Pneumodermon are lobed, and at the 

 hinder part of the body ; in Spongiohranchia they form a 

 prominent ring near the end of the body ; in Tricliocyclus 

 a ciliated ring round the middle of the body ; and in Pe- 

 lagia they are indistinct or wanting. 



Genus PNEUMODERMON, Cuvier. 



Body oblong, elongated or subglobose ; fins small and 

 rounded, on each side of the head. Gills in the form of a 

 four-lobed leaf, at the extremity of the body. 



Syn. Pneumoderma, Peron and Lesueur. ^Egle, Ohen. 



Ex. P. violaceum, D'OrUgny^ pi. 7, fig. 9. 



The Pneumodermon, like other genera of this class of 

 animals, is by no means shy in its habits, and swims ac- 

 tively about in the vessel of water in which it is confined, 

 but when touched folds its fins upon its body and falls to 

 the bottom, rolled up into a little ball : there are four 

 species described. 



Species of Pneumodermon. 



pellucidum, Quoy and Gaim. rubrum, Quoy and Gaim. 

 Peronii, Lam. violaceum, D'Orb. 



Genus SPONGIOBRANCHIA, D'Orbigny. 



Body fusiform ; head distinct ; mouth with long appen- 

 dages sometimes furnished with sessile suckers. Wings 

 two, entire, with a foot-like appendage. Gills in a promi- 

 nent spongy ring on the end of the body. 



Ex. S. australis, D''Orhigny, pi. 7, fig. 10. 



This genus is remarkable for the near approximation it 

 makes to the Cephalopods, the cephalic arms or appen- 



