334 GENERAL ZOOLOGY 



modern devil-fishes. On land insects were abundant and 

 had probably come to take some part in the pollination of 

 plants. 



TERTIARY AGE 



Eocene Period. There were great changes of scene be- 

 tween the Cretaceous and Eocene. Many old types of 

 reptiles and other animals were extinct; mammals now 

 became the most important land animals. The ancestral 

 stocks of rodents, elephants, bats, ruminants, whales, 

 carnivores, edentates, and insectivores had already reached 

 some degree of differentiation. There were also other 

 primitive mammalian strains in existence which have since 

 become extinct. Birds without teeth were present in 

 considerable numbers and variety. The reptiles, amphi- 

 bians, and fishes all had a more modern aspect. Such types 

 as lizards, snakes, tailless amphibians, and herrings were 

 prevalent. Among the invertebrates also there were hermit 

 crabs, and other specialized modern types. 



Oligocene Period. There were now a number of types 

 of hoofed animals in existence. Among the survivors of 

 the strange herbivores of Eocene times, the rhinoceros- 

 like titanotheres were perhaps the most remarkable, but 

 they were all extinct before the beginning of the next period. 

 The true rhinoceros stock was as yet hornless; the horses 

 had increased to the size of foxes and their feet showed some 

 degree of specialization toward the reduction of toes; pigs 

 were small creatures with four usable toes on each foot; the 

 ruminants were without horns, even the deer. Among the 

 carnivores the sabre-tooth cats were perhaps the most 

 striking though they had not yet attained their greatest size. 

 These animals had the upper canines greatly elongated. 

 Civet cats and carnivores related to modern weasels were 

 in existence. Primate remains have also been found in 

 the deposits from this period. The first pioneers of the 

 Primates were primitive lemur-like animals. Among the 

 birds there were divers like modern grebes, cormorants, 



