244 THE AGE OF MAMMALS 



northern Europe. After the Lower Burdigalian, which is close to the 

 OHgocene in character, palms cease north of the Alps, and toward the 

 end of the Miocene there was a furth(^r fall in temperature, especiall}^ in 

 the Arctic regions.' The absence of palms north of the Alps- is paralleled 

 by their absence in the entire Rocky Mountain region of America from 

 Colorado northwest. In consulting the earlier treatises of Saporta (1867) ^ 

 and Heer (1865) '' it is important for the student to note that at the time 

 these works were written, the entire warmer Oligocene Period was em- 

 braced within the Miocene. We have few records of the development of 

 grasses, but there is no question that Kowalevsky's generalization (1873), 

 based upon the structure of the feet and teeth of mammals, that the Miocene 

 was characterized by an increase of grassy plains, was correct; yet it is 

 remarkable that only at the close of the Miocene of Europe do mammals 

 with hypsodont, grazing teeth and stilted or cursorial limbs suddenly ap- 

 pear in large numbers; they are Oriental or exotic forms, which, however, 

 were tempted to enter Europe by climatic and floral conditions to which 

 they had become perfectly adapted in Asia and North America. If the 

 palaeontologist, observes Kowalevsky,^ will imagine himself in the close of 

 the Miocene, he will see great changes going on. Omnivorous forms are 

 becoming graminivorous, the method of chewing is changing from a vertical, 

 biting movement, to a horizontal, grinding one; and to meet these new 

 conditions of feeding it is necessary that more durable teeth should be 

 developed. The low teeth are replaced by columnar ones. It is in these 

 anatomical changes that we find the surest proof of the existence of the 

 great grassy plains and of the development of silicious plants. "How- 

 ever," observes Gaudry,^ "grasses did not form a very large element of 

 the vegetation even at this time." This was the beginning of the period 

 of dry, grassy plains, similar to those of recent Africa, and extending through, 

 the greater part of the Pliocene. 



Continental connections. — The emergence of the continents progressed 

 in the Miocene. The great Mediterranean Sea of Europe and southern 

 Asia was consequently reduced, and Africa, to the east at least, w^as united 

 with Europe, permitting the northward migration of the mastodons and 

 dinotheres. America was broadly united with eastern Asia, and the 

 shutting off of the warmer southern currents from the polar region prob- 

 ably marked the commencement of a cooler northern climate. South 

 America still remained separate; at least, there is no evidence of a faunal 



1 Schimper und Schenk, Palseophytologie, 1890, p. 820. 



^ Palms and camphor trees are recorded in the Middle Miocene beds of CEningen, 47"^ 

 N. lat. 



' See Bibliography. 



^ Kowalevsky, V., Monographic der Gattung Anthracotherium Cuv. und Versuch einer 

 natiirlichen Classification der fossilen Hufthiere. Palceontographica, n.s., 2, 3, (XXII), 1873, 

 p. 270 fol. 



^ Gaudry, A., Animaux Fossiles du Mont Leberon (Vaucluse). Etude sur les Vertdbres, 

 p. 79. 4to, Paris, 1873. 



