232 



GEOLOGICAL SUCCESSION OF ANIMALS 



Echini, among them Cidaris, (e,) with large spines, and 

 several other types not found before, as, for example the 

 Dysaster, (f) and the NucleoUtes, (g.) 



488. The fauna of the Cretaceous period bears the 

 same general characters as the Oolitic, but with a more 

 marked tendency towards existing forms. Thus, the Ich- 

 thyosauri and Plesiosauri, that characterize the preceding 

 epoch, are succeeded by gigantic Lizards, more nearly 

 approaching the Reptiles of the present day. Among the 

 Mollusks, a great number of new forms appear, especial- 

 ly among the Cephalopods,* some of which resemble the 



Fig. 164. 



Gasteropods in their shape, but are nevertheless cham- 

 bered. The Ammonites themselves are quite as numerous 



Fig. 165 



as in the Oolitic period, and are in general much orna- 

 mented, (.) The Acephala furnish us, also, with peculiai 

 types, not occurring elsewhere, Magas, (a,) the Inoceramus 



* (0 Ammonites; (b) Crioceras ; (c) Scaphites ; (d) Ancyloceras 

 (e) Hamites- (/) Baculites; (g] Turrilites. 



