132 



ORDERS OF FISHES. 



others of the Teleostei as well Moreover, some of the 

 Ganoids {Spatularia) have the skin quite naked; while 



Fig. 499. — A, iepidosfcws ossews, the "Gar-pike" of the American lakes; b, Aspkiorhyii- 

 chiis, restored (after Agassiz), a Jiirassie Ganoid allied to Lepidosteus, but having a homo- 

 cereal tail. 



others {Acipenscr and Bca])%rliynclius) have detaclied dermal 

 plates of true bone. 



3. As to \hQ, fins, both pectorals and ventrals are usually 

 present, and the ventrals are always placed far back, in the 

 neighbourhood of the anus, and are never situated in the im- 

 mediate vicinity of the pectorals. In some living and many 



Fig. 500.— Ganoid Fishes, a, Polypterns (recent); b, Ostcokpls (extinct), n, One of the 

 pectoral fins, .showing the fin-rays arranged round a central lobe ; 6, One of the ventral 

 fins ; c, Anal fin ; d, Dorsal fin ; d', Second dorsal fin. 



extinct forms the fin-rays of the paired fins are arranged so 

 as to form a fringe round a central lobe (fig. 500). This 



