On the Classification of Mammalia. 171 



Now there are other groups which we place on still an- 

 other level above the normal types, although not of an 

 absolute superiority. Their place can be nowhere else ; their 

 history must follow that of the normal types from which 

 they proceed : the Bradipodidai (or sloths), arising from the 

 herbivorous stem of Edentata ; the Sciuridai (or squirrels), 

 arising from the stem of Rodentia ; the Cheiroptera (or bats), 

 arising from the stem of Insectivora ; and the Quadrumana 

 (or monkeys), arising from the stem of Carnivora. 



We consider these as so many shoots of the mammalian 

 tree, which went beyond the vital sphere of activity of the 

 class ; in other words, deviations from the normal develop- 

 ment of the class. 



III. § 1. Let us return now to some of the groups mapped 

 down on our chart of the ideal gradation, and state in a very 

 brief manner their most striking zoological features and rela- 

 tionships. 



To begin with Edentata, which we concluded were the 

 lowest of the class : when looking at those creatures amidst 

 the other groups, we cannot help being strangely struck by 

 their singular physiognomy, and the still more astonishing 

 association of characters, which appear sometimes rather 

 borrowed from other classes, than as belonging to that of 

 Mammalia. We need only call to mind the water-mole 

 {Ornithorhyncus) of New Holland, the pangolins (Manis) of 

 Asia and Africa, the anteater (Myrmecophaga) and arma- 

 dillos (Dasypus) of South America, the aard-vark (Orcytero- 

 pus) of the Cape of Good Hope, and the sloths of tropical 

 America, which constitute the three orders Monotremata, 

 Edentata proper, and Tardigrada ; the one as strange as the 

 other. 



The Monotremata exhibit the lowest grade of mammalian 

 organization. They are ovoviviparous ; the young are with- 

 out uterian connection with the mother, but they are suckled 

 by the latter. In that respect they approach nearest to birds 

 and reptiles ; the structure of their sternum and shoulder, 

 also, presents a great resemblance to the same parts in 

 lizards and ichthyosauri. Their position at the bottom of the 



