MESOZOIC AND CENOZOIC LIFE 439 
of mammals, such as the cave-bear and mastodon, which 
have since become extinct. 
While the point cannot be supported by definite proof, 
ee 
Fic. 258. 
A group of Eocene fossils. 
(1 and 2, Crassatella alta; 3, Cerithium giganteum; 4 and 6, Venericardia plani- 
costa; 5, Lacinia alveata; 7 and 8, Ostrea selleformis.) 
