314 



HISTORICAL GEOLOGY 



reached their culmination in size at least, some having grown to a 

 length of ten to twenty inches and a width of six or eight inches 

 (Fig. 193). Cephalopods, as we have learned, diminished remark- 

 ably at the close of the Cretaceous, a very few only of the Ammo- 

 nites and Belemnites having straggled into the Tertiary, while the 

 Nautiloids (e.g. Nautilus) were more diversified and widespread 



Fig. 193 



Large Oyster shells, Ostrea georgiana, in Eocene strata of Georgia. 

 L. W. Stephenson, Geol. Sur. Ga., Bui. 26.) 



(After 



than now. The Dibranchs were of the modern Squid and Cuttle- 

 fish types. 



Among Arthropods all the principal groups except the simplest 

 (e.g. Trilobites and Eurypterids) were represented, the Crabs 

 among the Crustaceans having become numerous and varied. 

 Insects are known in far greater numbers and variety than from 

 any preceding period. All the important groups or orders were 

 represented, including the highest, such as Moths, Butterflies, 



