Alleu.] 3G0 [May 3, 



Remarks on the Pronghorn (Aritilocapra Americana). 



By Harrison Allen, M.D. 



{Read before the American Philosophical Society, May 3, 1SS9.) 



While observing tlie movements of the two examples of the pronghorn, 

 now in the Zoological Garden in Philadelphia, I noticed that the foot, iu 

 receiving the support of the body, exhibited the first phalanx partially ex- 

 tended upon the metapodium, and the second partially flexed upon the 

 first. The movement was marked in a greater degree in the pronghorn 

 than in any other ruminant in the Garden, which contains several speci- 

 mens of the Old World antelopes. 



It occurred to me that a heavier bulk of trunk would tend to force the 

 phalanges nearer the ground, and that the digitigrade plan of progression 

 be converted in this way into a phalangigrade. Comparing the foot of 

 the pronghorn with that of the llama in which such a change has actually 

 occurred, it was seen that in some respects the two animals move the feet 

 in similar ways. Notably in this regard is the manner of turning the 

 trunk on a limb which, in each of the animals named, is being used for 

 support. The limb permits a marked degree of torsion to take place before 

 the foot is lifted, and the twist to occur for the most part on the inner 

 hoof, while the outer hoof describes an excursus. 



Such conclusions led me to compare other parts of the hind limb with 

 each other as they are found in the camel, the llama and the pronghorn. 

 I found the several parts resembling each other in the following particu- 

 lars, as distinguished from their congeners : While the thigh is exsert in 

 the camel and llama, it is partially so in the pronghorn. The fold of integu- 

 ment in the pronghorn which passes from the trunk to the limb reaches it 

 at a point directly above the knee. In the deer it reaches it at the knee, 

 or over the tuberosity of the tibia, and in the bovine group still further 

 down. In the Virginian deer the fold answers to the separation of the 

 venter color from that of the upper part of the side of the body and of the 

 dorsum. In the pronghorn, the camel, and tne llama, the fold answers to 

 no localization of color. The camel, llama and pronghorn also resemble 

 one another in the width between the thighs as seen from behind, and in 

 the great inward inclination of the legs at the ankles. 



These resemblances were so striking that I was induced to compare the 

 crania of these animals with one another. I found that they agree in hav- 

 ing the lachrymal bone* excluded in great part from the floor of the orbit, 

 and iu having the bone extended posteriorly to a less degree than the 

 maxilla. In other ruminants (except the Chilian deerf) the lachrymal 

 bone comprises the orbital floor and extends posteriorly beyond the max- 

 illa. 



* The peculiarities of the lachrymal bone are of special importance in determining 

 the value of craniological characters. I have found its shape aud relations of great in- 

 terest in studying the mammalia, 



t Pudua huinilis. 



