72 MIOCENE FAUNA. 



the Anthracotheria. The proportions of the families are there- 

 fore very similar. In the Swiss Eocene, and likewise in the 

 Miocene fauna, the Pachyderms form nearly one half of the 

 Mammalia ; the Ruminants in the Eocene constitute one fourth, 

 and in the Miocene between one fifth and one sixth. The her- 

 bivorous animals consequently form by far the most important 

 part of the fauna, and the Garni vora are much fewer than at the 

 present clay; they constitute, in the Miocene period, only one 

 ninth or one tenth, whilst they are about one fifth of the existing 

 fauna. 



The Mammalia are primarily divided into two great sub- 

 classes the Didelphya, which place their very imperfectly deve- 

 loped young in a ventral pouch, and carry them about with 

 them ; and the Monodelphya, which are destitute of this appa- 

 ratus. The former are further distinguished by important ana- 

 tomical characters, which show that they occupy the lowest 

 grade in the history of the development of the Mammalia. At 

 present they are, with the exception of a few species, confined 

 to the southern hemisphere, and, by means of the kangaroos 

 and opossums, they give a peculiar character to its fauna. An 

 opossum (Didelphys Blainvillei, Gerv.) has been discovered in 

 the Swiss Miocene near Vermes in the valley of Delsberg. The 

 opossums are small rat-like animals, with long, scaly, prehensile 

 tails, and pointed heads with wider mouths. They live on in- 

 sects, birds, and reptiles. The young of many species, when 

 they have quitted the ventral pouch, creep on to the back of 

 their mother and hold fast by twisting their tails round hers. 

 The species of the genus, which are numerous, occur in Peru and 

 Brazil, and one or two of them in tjie south of the United States. 



All the other Mammalia of the Swiss Miocene belong to the 

 Monodelphya, the most important Miocene family of which is 

 that of the Pachydermata. It includes not only the greatest 

 number of species, but also the largest ones, equalling in size 

 the largest of the land mammals of the present day. The Swiss 

 fauna possessed fifteen genera, and at the same time a variety of 

 forms such as no part of the earth of such small dimensions can 

 now present. The group of the tapirs is represented by the 

 genera Pal&otherium and Tapirus. Of Palceotherium (P. 

 Schinzii, Meyer) a fine lower jaw with teeth has been found in 



