2 7 6 



HISTORICAL PALAEONTOLOGY. 



the great modern order of the Bony Fishes or Tcleosteans 

 makes its first appearance in the Upper Cretaceous rocks, 

 where it is represented by forms belonging to no less than 

 three existing groups namely, the Salmon family (Sal- 

 monidce), the Herring family (Clnpeidce), and the Perch family 

 (Percidce), All these fishes have thin, horny, overlapping 



Fig. 208. i, Beryx Lewesiensis, a Percoid fish from the Chalk ; 2, Osnieroidcs 

 Mantelti, a Salmonoid fish from the Chalk. 



scales, symmetrical (" homocercal ") tails, and bony skeletons. 

 The genus JBeryx (fig. 208, i) is one represented by existing 

 species at the present day, and belongs to the Perch family. 

 The genus Osmeroides, again (fig. 208, 2), is supposed to be 

 related to the living Smelts (Osmerus), and, therefore, to 

 belong to the Salmon tribe. 



No remains of Amphibians have hitherto been detected in 

 any part of the Cretaceous series ; but Reptiles are extremely 

 numerous, and belong to very varied types. As regards the 

 great extinct groups of Reptiles which characterise the Meso- 

 zoic period as a whole, the huge " Enaliosaurs " or " Sea- 

 Lizards" are still represented by the Ichthyosaur and the 

 Plcsiosaur. Nearly allied to the latter of these is the Elas- 

 mosaurits of the American Cretaceous, which combined the 



