AGE UF FISHES. 



207 



: -^v^lK2, 



Fig. 117. 



cle. The scales, 6, have a simple and smooth margin, 

 and their outer surface is often variously ornamented. 

 In this order are the salmon, the carp, and the pike. 



I shall have occasion to refer to these orders hereaf- 

 ter. Suffice it to say now that the placoids and ganoids 

 had their greatest developments in the Palaeozoic ages, 

 and that there are few of them at the present time, while 

 the ctenoids and cycloids came on at a later age, and 

 abound in the waters of the present period. Four fifths 

 of the present fishes belong to the ctenoid and cycloid 

 orders, the remaining fifth consisting of placoids, with a 

 small number of ganoids. 



300. Coccosteus, Pterichthys, and Cephalaspis. The 

 fishes of the Devonian age whose names I have here 

 given are ganoids, having very peculiar characteristics. 

 The Coccosteus, or "berry-bone," 1, Fig. 118 (p. 208), has 

 the largest part of the body incased in a box-like cover- 

 ing of bony plates, upon which there are berry-like projec- 

 tions. The Pterichthys, or " wing-fish," 2, which Hugh 

 Miller, its discoverer, termed the characteristic organism 

 of the old red sandstone, is so extraordinary that Agassiz 

 says of it that " it is impossible to find any thing more 

 eccentric in the whole creation." On the head was a 



