218 MAMMALS. 



The facts relating to si^ecial faunas in the eocene and early miocene times seem to show 

 that when the peculiar facies was imjjressed on the famia and flora of any country it was at that 

 time isolated from all other countries ; that when it was united to other lands, the typical form 

 spread into them under the same, or nearly the same form. 



We see this in North and South America, which have at different times been separated and 

 again united. Wlien isolated, the Edentate and Marsupial fauna, considered characteristic of South 

 America, increased and flourished there. When united it overflowed and spread into North 

 America. This is proved by the fossil remains of Edentate animals found in that country, and 

 by the persistence there to the present day of small species belonging to that and the marsupial 

 type. 



But if the affinity of the North and South American Edentata proves former continuity, so must 

 that of the Old-world and the New-world species. This affinity is something very different in 

 degree from that of which we have been sf)eaking. The Old-world species are of a peculiar type. 

 There is the same general structure, and the same idea shows itself in various ways : but it has 

 taken a different direction. In the New-world Armadillos, the animal is enveloped, more or less, 

 in impervious horny plates, under which it can obtain protection. The Old-world Pangolins are 

 clothed, on the other hand, with scales. One species, the Cape Orycteropus, is not ; it is merely 

 clothed with hair ; but both Pangolin (Manis) and Orycteropus are Ant-eaters, and truly represent 

 the Ant-eaters of South America, which have coarse hair too ; but the Pangolins have borrowed 

 the idea of their horny cloak from the toga of the Armadillo, the cousin of the American Ant- 

 eater. 



Whence have these creatures come ? some common ancestor has doubtless worn a coat made 

 of such stuff. The general structure of the Moxotrf.mata comes nearer to that of the Edentata 

 than to that of any other animal. They have often been classed together, or next each other. 

 Cuvier formerly so classed them. Giebel and others, in our own times, do so now ; and although 

 the Monotremes are more generally placed after the MarsujDials, and next the Birds, in right of 

 their duck-bill and lower organisation, even those who place them there admit that the Edentata 

 possess a similarly low organisation.* The Echiuna bears a coat so far similar to that of the Pan- 

 golin, that it is horny ; only, instead of horny scales, it has solid horny quills. We have not qmte 

 the same barrier here raised up which met us in our attempts to trace the Placental animals 

 directly from the Marsupial, viz. the impossibility of believing that nature has several times re- 

 peated the same change. In the Monotremata we find the change half operated to our hand. 

 The marsupial pouch has disappeared, — the marsupial bones remain. 



We may thus suppose the Edentata to be not very distantly related to the Monotremes. Their 

 common ancestors may have lived in the Pacific Contiaent which we have suiDposed at one time 

 to have existed in the South Seas, or between Australia and Africa. Whether there was a com- 

 munication between America and this suj^posed land, or whether the species had to arrive by 

 Africa, and thence across the Atlantic, by land then in existence, is one of those problems for the 

 solution of which we have no sufficient data. I shall only notice as possibly haviag a bearing on 



* "The unusual number of three-and-tweuty pairs of cerebral development, the absence of medullary canals in 



ribs, forming a very long dorsal, with a short lumbar, the long bones in the Sloth ; and by the greater tenacity 



region of the spiue, in the two-toed Sloth, recalls a lacertine of life, and long enduring irritability of the muscular fibre 



structure. The same tendency to an inferior type is shown in both the Sloths and Ant-eaters. — Owen, in " Proc. 



by the abdominal testes, the single cloacal duct, the low Linn. Soc.'" ii. ii3, 1857. 



