514 



CENOZOIC ERA— AGE OF MAMMALS. 



Among bivalve shells, common forms of the present day, such as 

 the oyster, the clam ( Venus), the scallop-shell (Pecten), etc., were very 

 numerous, and some of very large size. Oysters especially seemed to 

 have reached their maximum development in the Tertiary. The Ostrea 

 Georgiana (Fig. 863) was ten inches long and four wide ; the Ostrea 

 Oaroliniensis was of equal size, but shorter and broader. A specimen of 

 the Ostrea Titan of California and Oregon now lies before us, which by 

 measurement is thirteen inches long, eight wide, and six thick (Fig. 

 870), and a specimen of Pecten Cerrocensis of California, nine inches 

 across (Fig. 871). Among . univalves also nearly all the forms are 

 familiar. The illustrations are taken from the Eocene and Miocene. 

 The Pliocene shells are almost undistinguishable from living shells, 

 except by the practiced eye. It seems useless to give them in an ele- 

 mentary work. 



Insects. — There are several interesting points connected with this 

 class which must not be omitted. We have usually found insects abun- 

 dant in connection with luxuriant vegetation. During the Miocene, 

 phenogamous vegetation was even more abundant than now ; there was 

 also extreme fullness of insect-life. All orders, even the highest, viz., 

 Lepidoptera (butterflies — Fig. 878) and Hymenoptera (bees, ants, etc. 

 — Fig. 877), were represented. 



Fig. 877.— Insects of European Miocene (after Heer): a, Apis Adamitica; b, Ponera veneraria 

 male, b' female; c, Vespa atavina; d, d. Ammophila inferna; e, Imhoffia pallida; /,/',/", For- 

 mica lignitum— female, male, and worker; g, Myrmica tertiaria; h, Ichneumon infernalis; i, 

 Xilocopa senilis; k, Bombus Jurinei; I, Scalea saussureana. 



In the Miocene of Europe, 1,550 species of insects have been found ; 

 and of these more than 900 species at (Eningen in a stratum only a few 

 feet thick (Lyell). In places the stratum is black with the remains of 

 insects. The same stratum is also full of leaves of Dicotyls, of which 



