MAIVBIALIAN ORDERS. 



283 



Pcrissodactjie hoofed limb 

 Hind leg, Rliiaoceros. 



The present order rests with the Ungulata mainly upon its 

 hoofs : the dentition and some other particulars of the organisa- 

 tion of the Elephant, indicate an affinity to the Rodentia : the 

 abdominal testes, the two precavals and exposed cerebellum, are 

 characters of the inferior subclasses : but the cerebrum, concomi- 

 tantly with the bulk of the mammal, is large and well convoluted, 

 and the psychical qualities correspond. The 

 earliest known evidences of Proboscidian Un- 1^3 



gulates are from miocene strata. 



The typical Ungulate quadrupeds are di- 

 vided, according to the odd or even number of 

 the toes, into Perissodactyla and Artio- 

 DACTYLA.^ In the former the hoofs may be 

 one (Horse) or three {Rhinoceros, fig. 163): 

 in the latter the hoofs may be two (Giraffe), 

 or four (^Hippoijotamus), or two functional and 

 two rudimental (most Kuminants, fig. 164). 



In the Perissodactyle Ungulata — odd-toed 

 in regard to the hind-foot in all, and with the 

 fore-foot unsymmetrically tetradactyle in the Tapir — the dorso- 

 lumbar vertebrse, fig. 165, C, D, differ in number in different species, 

 but are never fewer than twenty-two ; the femur has a third 

 trochanter, ib. 65 ; and the medullary artery 

 penetrates the back-part of its shaft. The 

 fore-part of the astragalus is divided into two 

 very unequal facets. The os magnum and the 

 digitus medius which it supports are large, in 

 some disproportionately so, and the digit is 

 symmetrical : the same applies to the ectocu- 

 neiform and the digit which it supports in the 

 hind-foot. If the species be horned, the horn 

 is single : or, if there be two, they are placed 

 on the median line of the head, one behind the 

 other, each being thus an odd horn. The nasals 

 expand posteriorly.^ There is a well-developed post-tympanic pro- 

 cess which is separated by the true mastoid from the paroccipital 

 in the Horse, but unites with the lower part of the paroccipital 

 in the Tapir, and seems to take the place of the mastoid in the 

 Rhinoceros and Hyrax. The hinder half, or a larger proportion 



164 



Artiodactyle hoofed limb ; 

 Hind leg, Antelope. 



the chorionic bag, by which it derived additional attachment to the uterus, in the 

 Elephant. Lxiir. p. 347, ph xvi. 



' JFrom Trepto-troSoKTi/Aos, qui digitos habct imparcs numero ; and &pTios, par, 

 MktvAos, digitus. - LXXi. p. 398. 



