Fossil Fishes 1 1 5 



considerably diversified. This conclusion is so remarkable, and 

 the resemblances to Devonian types are so striking, that we 

 naturally wonder whether these rocks are really Ordovician. 

 When Wolcott's specimens were first brought to light, Professor 

 James Hall said that he would certainly have referred them to 

 the Devonian, but for the accompanying invertebrate fauna. 

 When I published the account (1913) of the Ohio City find, I 

 queried the reference to Ordovician, and thereby exposed myself 

 to criticism by more than one paleontologist. The students of 

 the accompanying invertebrates are all agreed that the rocks 

 can only be Ordovician, and this opinion must be accepted in 

 the light of the available evidence. 



Passing over a vast interval of time, we may now consider 

 the fishes of the Cretaceous epoch, when the place occupied by 

 our present foothills was the shore of a wide sea. The American 

 Mediterranean, or inland sea, covered the region east of our 

 front range, and also existed west of it, in the territory between 

 the Rockies and Sierra Nevadas. There were of course changes 

 of level, with corresponding changes in the extent of the waters, 

 but the general fact remains that there was a great expanse of 

 relatively shallow warm ocean, connected southward with the 

 Atlantic. In such an area, life was sure to be abundant, and the 

 opportunities for the increase of shallow water and littoral types 

 were far greater than at present. Today if we color on a map the 

 shallow water areas about North America, they appear like rivers 

 running mainly north and south along the coasts; narrow belts 

 in which the development of life is restricted by the land on one 

 side, the deep sea on the other. North and South the changes of 

 temperature interfere with the spread of particular genera and 

 species. The wide inland seas of Cretaceous time seem to have 

 afforded opportunity for the evolution of the various families of 

 modern bony fishes, so that the student may expect to see the 

 earliest representatives of various familiar groups. Not only 

 were the species numerous, but some were of great size. Won- 

 derfully preserved specimens of the gigantic Hypsodon audax of 

 Leidy are to be seen at the University of Kansas and in the 

 British Museum; we can but speculate on the fate of the angler 

 who might have hooked such a monster! Unfortunately the 

 fossil skeletal remains of our Cretaceous fishes are abundant only 



