l8 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [BuU. 



as a specialized derivative. Recently described remains of Pro- 

 topterus from the African Tertiary present an astonishing like- 

 ness to Sagenodus, as regards the dentition. 



Yet another group of fishes, representing a still higher grade 

 than any of the foregoing, makes its first appearance during the 

 Devonian, but does not begin to acquire dominance until the 

 Carboniferous. This is the great group of Actinopterygians or 

 "ray-finned" fishes, to vi^hich by far the greater number of 

 modern forms belong. From the Devonian onward until the 

 close of the Permian, this higher grade of fishes was represented 

 by a single family of primitive Chondrostei, whose degenerate 

 descendants finally passed over into modern Sturgeons. It is 

 probable that the short-lived family of the Catopteridse, which 

 gained a wide distribution in the Trias, is an offshoot of the 

 tribe of primitive Sturgeons; and it is noteworthy that the de- 

 cline of the latter began simultaneously with the rise of the 

 next higher suborder, or Protospondyli. No links are known 

 connecting this suborder with the Chondrostei, hence in the 

 present state of our knowledge, the Sturgeon tribe and the Pro- 

 tospondyli are distinctly demarcated. During the Trias the 

 Protospondyli are represented by the important and truly cos- 

 mopolitan family of Semionotidas, which, with the previously 

 mentioned Catopteridae, form the chief constituents of our local 

 Triassic fish fauna. The only modern representatives of this 

 suborder are the bow-fin and garpike (Amia and Lepidosteus), 

 both confined to the fresh waters of North America, and ex- 

 hibiting the long-bodied shape of senile or decrepit dereHcts. 



Associated with members of the preceding suborder (Pro- 

 tospondyli) in rocks of the Upper Trias are found a few fishes 

 having a remarkably modern aspect, and characterized not only 

 by a complete vertebral column, but also by a simplified lower 

 jaw, which consists of but two pieces on each side. The fore- 

 runners of the Isospondyli, as this suborder is called in allusion 

 to the circumstance that the vertebrse are simple, without being 

 fused into a group behind the head, scarcely differ in grade from 

 the modern herring tribe. Among typical representatives may 

 be mentioned the genera Pholidophorus and Leptolepis, ranging 

 throughout the Triassic and Jurassic. The group- displays rather 

 feeble vigor until the beginning of the Cretaceous, when it 



