20 



FOSSIL FISHES. 



In the genus Pterichthys (Figs. 26 and 27) there are two peculiar 

 arras, or anterior fins, articulated to the sides of the body, just 

 behind the head ; the tail is covered with scales, and supports the 

 dorsal fin. 



Fig. 27. 



Fig. 26. 



Fig. 26.— Dorsal surface of Pterichtkys Milleri (after Pander), Old Red Sandstone, Scotland. 

 Fig. 27. — Pterichthys cornutvs, Agassiz, Old Red Sandstone, Scotland. 



The gigantic Asterolepis seems to have been allied to Pterichthys. 



In Coccosteus (Figs. 28 and 29) the tail was destitute of scales, 



but very distinct neural and haemal spines are seen with interspinous 



Fip. 2S. — Coccosteus (after Pander), side-view, Old Red Sandstone, eh Position of the 



chorda dorsalis, or notochord. 



bones, supporting a dorsal and anal fin, but no vertebrae have been 

 observed, so that the notochord must have been persistent. 



Prof. Newberry has described a huge Placoderm (Dinichthys) 



