226 MAMMALS. 



I have made these remarks by way of proving that these Mcgatherold animals must, 

 from their habits and mode of life, have been fitted for a very warm, damp climate, similar to, 

 and, perhaps, even hotter than that of the Brazilian forests in the present day ; the habits which 

 have, I think, been successfully proved to be theirs being inconsistent with anything but a tropical 

 climate. It is plain, that whole tribes of these great creatures, twelve and eighteen feet in 

 length, could never have been supplied by loaves and twigs obtained by the wasteful j)roccss of 

 uj)rooting trees, except in a country where the vegetation was most luxuriant and the growth 

 exceptionally rapid. 



It seems not improbable, therefore, that it is to the glacial cold that we owe the extinction of 

 these larger Edentata ; for, as Professor Owen remarks, the chemical conditions of life are such, that 

 the larger an animal is, the less resistance can it make, and the more readily does it succumb to any 

 unfavourable change ; which is one of the reasons why we find small species surviving, while the 

 larger species have, in many instances, disappeared, and are only now to be met with in a fossil 

 state. 



(2.) Sloths. (Map 61.) The Takdigrada inhabit the north-east of South America, reaching, in 

 the north, almost to the Isthmus of Panama, on the west to the Andes, and on the south to the south 

 of Brazil, but not into Paraguay. A new species of two-toed Sloth, Ch(1lcepus Hoffjianni, has 

 lately been found in Costa Rica, and described by Dr. Peters, who has discovered in it an abnormal 

 number of cervical vertebrae — in the reverse direction from the three-toed Sloths. They have nine 

 cervical vertebrae instead of seven. This animal has only six. 



II. Armadillos. (Map 60.) Those little mailed creatures, whose restless activity is so attractive 

 to the public in our Zoological Gardens, were represented in the pliocene and post-pliocene ages by 

 animals which must have been considerably more staid in their demeanour and deliberate in their 

 movements ; for thej' were almost as large as the Megatherium, and enclosed entirely in an imj-ielding 

 bony case, bearing some resemblance both in shape and pattern, on a great scale, to a portion of the 

 shell of an Echinus or Sea Urchin. The existing Armadillos, as the reader knows, are invested 

 in a succession of bands of jointed plates, which, like a suit of scale armour, conforms itself to the 

 motion of the body, and allows the animal, when it chooses, to roll itself up into a ball, which is more 

 or less protected, according to the number and breadth of the bands ; and these, like the band of tlie 

 plated armour of our defended ships, are always applied round the most vital parts of the body. 

 But the extinct species, the Glyptodons, were wholly enclosed in theirs, except on the belly. Even 

 the tail had a coat of mail, and the head was protected by a piece of armour, like the chamfron 

 of a war-horse in the days of the Crusaders. The remains of these animals and of other extinct 

 Armadilloes have chiefly been obtained from superficial deposits near Buenos Ayres, and from the 

 bone-caves of Brazil. 



The living sjDecies have pretty much the same range, but they extend further to the south ; 

 one, D. MiNTJTUS, reaching as far south as 50° south latitude. The different species are local, 

 and the range of each not extensive. The difi'erence in the constitution of animals, as affecting 

 the origin of species, cannot be better illustrated than by the Armadillos and Ant-eaters of 

 South America. The Armadillos have apparently been susccjjtible to the most trifling change. 

 They appear not to have been able to pass from one district into another, — from Brazil into 

 Peru, or from Paraguay into La Plata, — without experiencing the change so keenly as to have set 

 up the action of the modifying jiower, and produced a change of species. Dr. Burmeister has 



