436 RECENT AND FOSSIL MAMMALIA. chap. xxii. 



clearly by how high a figure we must multiply the time in 

 order to express the distance between the Miocene Period 

 and our own days. 



Species of Mammalia recent and fossil. — Proboscidians. 



But it may perhaps be said that the mammalia afford more 

 conspicuous examples than do the mollusca, insects, or jjlants 

 of the wide gaps which separate species and genera, and 

 that if in this higher class such a multitude of transitional 

 forms had ever existed as would be required to unite the ter- 

 tiary and recent species into one series or net-work of allied 

 or transitional forms, they could not so entirely have es- 

 caped observation, whether in the fossil or living fauna. A 

 zoologist who entertains such an opinion would do well to 

 devote himself to the study of some one genus of mammalia, 

 such as the elephant, rhinoceros, hippopotamus, bear, horse, 

 ox, or deer; and, after collecting all the materials he can 

 get together respecting the extinct and recent species, 

 decide for himself whether the present state of science 

 justifies his assuming that the chain could never have 

 been continuous, the number of the missing links being so 

 great. 



Among the extinct species formerly contempoi^ary with 

 man, no fossil quadruped has so often been alluded to in this 

 work as the mammoth, Elephas primigenius. From a mono- 

 graph on the pi'oboscidians by Dr. Falconer, it appears that this 

 species represents one extreme of a type of which the Pliocene 

 Mastodon Borsoni represents the other. Between these 

 extremes thei-e are already enumerated by Dr. Falconer no 

 less than twenty-six species, some of them ranging as far 

 back in time as the Miocene Period, others still living, like 

 the Indian and African forms. Two of these species, how- 

 ever, he has always considered as doubtful, Stegodon Gancsa, 



