422 



DEVONIAN PERIOD 



true fish, was represented by the singular little Palaospondylus 

 (Fig. 370), which represents the vertebrate idea in great simplicity. 



Fig. 369. Reconstruction of the head and trunk of Tremataspls, seen from 

 above. Natural size. (After Patten.) 



Fig. 370. Palceospondylus gunni, restored by Traquair; from the Old Red 

 Sandstone, Caithness, Scotland. (After Dean.) 



It had a slender column of vertebrae, modified at one end into a 

 head and finned at the other for a tail, without ribs, paired fins, or 

 any suggestion of limbs. 



The fishes found in the supposed fresh-water deposits of the 

 Devonian exceed in number and variety those found in contempo- 

 raneous marine formations. Perhaps the strangest of them were 

 the arthrodirans (Fig. 371), probably related to the ancestors of 

 lung-fishes (Dipnoi) which reached their climax at about this time. 

 Ganoids were present, with many resemblances to amphibians, of 



