258 THE HISTORY OF CREATION, 
and in certain hoofed Rodentia (Subungulata) which live 
exclusively in South America. Beside smaller forms (for 
example, guinea pigs and gold hares) the Subungulata also 
include the largest of all Rodentia, namely, the Capybara 
Rats, which are about four feet inlength. The Rock Conies, 
which are externally very nearly akin to Rodents, especially 
to the hoofed Rodents, were formerly classed among 
Rodentia by some celebrated zoologists, as an especial sub- 
class (Lamnungia). Elephants, on the other hand, when not 
classed among Hoofed animals, were generally considered 
as the representatives of a special order which were called 
Trunked animals (Proboscidea). But the formation of the 
placentas of Elephants and of Hyrax agree in a remark- 
able manner, and are entirely distinct from those of Hoofed 
animals. These latter never possess a decidua, whereas 
Elephants and Hyrax are genuine Deciduata. Their placenta 
is indeed not of the form of a disc, but of a girdle, as in 
the case of Animals of Prey; it is very possible that the 
girdle-shaped placenta is but a secondary development of 
the discoplacenta. Thus, then, it might be thought that 
the Pseudo-hoofed animals have developed out of a branch 
of the Rodentia, and in a similar manner perhaps the 
Carnivora out of a branch of the Insectivora. At all 
events, Elephants and Hyrax in many respects, especially 
in the formation of important skeletal parts, of the limbs, 
ete, are more closely allied to the Rodentia, and more 
especially to hoofed Rodentia, than to genuine Hoofed 
animals. Moreover several extinct forms, especially the 
remarkable South American Arrow-toothed animals (Toxo- 
dontia), stand in many respects mid-way between Elephants 
and Rodentia. That the still living Elephants and Hyrax 
