138 



AR THR ODIRAN L UNG-FISHES 



but its pectoral appendages as well. The size of the 

 pectoral girdle is, of course, little proof that an anterior 

 pair of fins must have existed, since this may well have 

 been evolved in relation to the muscular supports of 

 plastron, carapace, trunk, and head. The inter-movement 

 of the dental plates, seen especially in Dinichthys, is a 

 further difficulty in accepting their direct descent from 

 the Dipnoans. 



