872 STRATIGRAPHICAL GEOLOGY. — [Boox VI. 
Mastodon. It was characterized also by troops of rhinoceros, hippo- 
potamus, and elephant; by large herds of herbivora, including 
numerous forms of gazelle, antelope, deer, and types intermediate 
between still living genera. Among these were some colossal 
ruminants, including a species of giraffe and the extinct genus 
Helladotherium, and other types met with among the Siwalik beds 
of India (Stvatherium, Fig. 424, Bramatherium). The Equide 
were represented by the existing Hquus, and by extinct forms, one 
of the most abundant of which was Hipparion (Fig. 418), like a 
small ass or quagga, with three toes on each foot, only the central 
one actually reaching the ground. There were likewise species of 
ox, cat, bear, and hyena, and numerous apes (Mesopithecus, Fig. 419), 
the remains of which have been met with 14° further north in 
Europe than their descendants now live. 
The advent of a colder period is well shown in the younger 

7 
7. LEE wy 
eS —— 
Fic, 419.—Mrsoprrurcus PENTELIcI (GAUDRY). 
Pliocene beds of England, where a number of northern mollusca 
make their appearance. The proportion of northern species increases 
1apidly in the next succeeding or Pleistocene beds. The Pliocene 
period therefore embraces the long interval between the warm 
temperate climate of the later ages of Miocene and the cold of 
Pleistocene time. According to Professor Prestwich, the evidence of 
change of climate derivable from the English Pliocene mollusca 
may be grouped as follows: 
Species now restricted to 
ere eee 
orthern Seas. Southern Seas. 
Norwich Crag . ; ; : : : 19 ; ; 11 
Red Crag . : ; ; ; : ; 23 : : 32 
White Crag. : ; ; ; ; 14 65 
The percentage of northern species in the White Crag is 5:0, in the Red 
Crag 10°7, in the Norwich Crag 14°6.! 
' Prestwich, Q. J. Geol. Soe. xxvii, Lyell, Antiquity ‘of Man, chap. xii, Searles 
Wood, ‘Crag Mollusea,” Palwont. Soc. 
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