294 



HISTORICAL GEOLOGY. 



Phiooderms (plate-skin); the latter, Lepido-ganoids (scale- 

 ganoids). Now, the Placo-ganoids are characteristic of 

 the Devoniaii> and the largest Devonian fishes, such as 



FIG. 212. 



FIG. 214. 



FIGS. 212-214. Devonian fishes Lepido-ganoids : 212. Osteolepis. (After Nichol- 

 son.) 213. Diplacanthus gracilis. (After Nicholson.) Sharks : 214. Cteuacan- 

 thus vetustus, spine reduced. (After Newberry.) 



the Dinichthys and Aster olepis, belong to this family. 

 The Lepido-ganoids continued after the Devonian, and 

 are still represented by gar-fishes, etc. The sharks of the 

 Devonian belong, all of them, to a family now almost 

 extinct, called Cestracionts (sharp tool, referring to the 

 spine). 



Affinities of Devonian Fishes. There are no living 

 representatives of the Placo-ganoids, but there are such 

 of the Lepido-ganoids. We herewith give figures of those 

 modern fishes which are most like the Devonian fishes. 



