478 Zoological Society. 



sions from each other. It is to our eminent Comparative Anatomist 

 that we are indebted, by the discovery of some new characters, and 

 the correction of certain former errors of observation, for the estabhsh- 

 ment of that mode of subdividing the Ungulata which first suggested 

 itself to Cuvier ; but there can be no doubt, that when the entire 

 anatomy of the order is investigated with this view, many constant 

 distinctions will yet be made apparent, and our appreciation of the 

 comparative degrees of affinity among its members will become clearer 

 as we proceed. ',tK[ .'xiT 



In taking up the subject as it has thus been left, I have first di- 

 rected my attention to the skull, as being that part in which the 

 greatest number of characters are presented at one view, and for the 

 study of which I have had the most ready opportunities ; and I now 

 propose to offer such results of my observations as I have been able 

 sufficiently to mature. In pointing out the characters of the skull 

 which distinguish these two grand divisions of the Ungulata, the 

 difi'erences will appear more striking if I consider the Perissodactyla 

 as they are restricted by Prof. Owen, namely exclusive of the Pro- 

 boscidian and other aberrant forms, which, though they agree with 

 them in the most essential characters, differ in many points of confor- 

 mation. 



The nasal bones in the Perissodactyla are gradually widened behind, 

 BO that their posterior angles approach the anterior margins of the 

 orbits, between which the suture which separates them from the 

 frontals runs more or less directly across the skull ; we may naturally 

 expect such a character to be masked by the singular modification 

 which these bones undergo in the Tapir ; but in the Artiodactyle di- 

 vision, even though the extreme points of the nasal bones occasionally 

 extend very high, or as in the Llama, and in the genus Cephalophorus 

 among the Antelopes, a sudden extension from their outer edge de- 

 scends a little on each side of the face, this decided character is never 

 manifested. 



The intermaxillary bones in the Perissodactyla, if there be teeth 

 developed in their median portion to a functional size, are always 

 deep enough to allow them to be vertically implanted, while in the 

 Artiodactyla, the teeth when existing in this bone always incline 

 towards each other, their roots being divaricated to allow the nasal 

 opening to extend down between them. In this group, with the 

 singular exception of the genus Hippopotamus, we find a distinct fo- 

 ramen above the orbit for the passage of the supraorbital nerve, with 

 a groove extending from it down the face ; while in the Perissodactyla, 

 it would appear as though this nerve would issue at a point more 

 towards the outside, since the foramen only exists in the Horse, in 

 which it is placed quite at the commencement of the postorbital pro- 

 cess, and has no groove continued from it. 



In the interior of the orbit, there is always, in the Artiodactyla, an 

 increased concavity of surface upon the anterior side about the junction 

 of the lacrymal and frontal bones ; and in the middle of this fossa, 

 upon the edge of the lacrymal somewhere between the ductus ad 

 nasum and the entrance of the infraorbital canal, a pit, most strongly 



