CRETACEOUS ANIMALS. 



483 



teeth, and also a tooth, natural size, of a gigantic pike, eight feet long, 

 from American Cretaceous, and a restoration of the same by Cope ; 

 also, two Teleosts from European Cretaceous. 



Fig. 805. 



Fig. 806. 



Figs. 801-806.— Cretaceous Fishes— Placoids : 804. Otodus (after Leidy). 805. Ptychodus Mor- 

 toni (after Leidy). Teleosts : 806. Portheus molossus— Tooth, natural size (after Cope). 



The Hybodonts were essentially a Mesozoic type ; the Squalodonts 

 are essentially Tertiary and modern. The two types coexist in the Cre- 

 taceous, the former passing out, the latter increasing, and finally dis- 

 placing the former. The accompanying figure (Fig. 810) represents the 

 succession, rise, culmination, and decline of the three families of sharks. 



Cope gives ninety-seven species of North American Cretaceous 

 fishes known in 1875. Of these, if we include the Chimera family, an 

 aberrant type of Placoids very common in the Cretaceous, forty-five 

 were Placoids. The rest are mostly Teleosts, for the Ganoids are rap- 



