LIFE OF TERTIAEY PERIOD 241 



Some of the older remains in South America, called Sparas- 

 sodonta, are believed to belong to the same or an allied sub- 

 order. They occur in beds of Lower Miocene age in Pata- 

 gonia ; and Mr. Lydekker holds them to be " undoubtedly 

 marsupials," allied to the Dasyuridic of Australia. One of 

 these has been named Prothylacinus, from the resemblance of 

 its jaw to that of the Tasmanian wolf (Thylacinus australis). 

 Other small species forming a distinct family, Microbiothe- 

 ridie, he also thinks were probably " minute polyprodont mar- 

 supials of Australian type." ^ 



In the later (upper) beds of the Eocene formation and the 

 early or middle Miocene, ancestral forms of many of our Mam- 

 malia have been found both in Europe and Xorth America ; 

 but these are so numerous, and their affinities in some cases 

 so obscure, that only a few of the prominent examples need 

 be given. One of these, whose skeleton is figured on page 243, 

 belongs to the family Anthracotheridae, which has affinities 

 with the pigs and the hippopotami, of which it seems to be 

 an ancestral form. The fossil remains of this group are found 

 in deposits of middle Tertiary age all over the northern hemi- 

 sphere. They have two, three, or four separate toes, and teeth 

 much like those of swine. 



Another family, the Anoplotheridae, contains a variety of 

 animals w^hich seem to be ancestral forms of the ruminants. 

 The genus Anoplotherium (Fig. 79) was one of the most re- 

 markable of these in having a full and continuous set of teeth 

 without any gaps, like that of the Arsinoitherium already 

 figured. 



1 Geog. Hist, of Mammals, pp. 111-112. From these facts and otliers re- 

 ferred to in my preceding chapter, Mr. Lydekker thinks that " it is difficnlt 

 to come to any other conclusion than that the ancestors of the Santa Crucian 

 polyprotodont marsupials reached the country either by way of the Antarc- 

 tic continent or by a land-bridge in a more northern part of the Pacific." 

 To avoid a break of connection in the present exposition, I have briefly 

 stated some of the difTieuliies in the way of such a theory in an Ap- 

 pendix to this chapter. Those who wish to see the whole subject of the 

 " Permanence of Oceanic and Continental Areas " more fully discussed are 

 referred to my volumes on Darwinism and Island Life. 



