LOXOLOPHODON AND UINTATHERIUM. 



29 



canine-incisor sockets. During the summer of 1878 we happily secured a com- 

 plete lower jaw unquestionably belonging to Loxolophodon, for with it was found 

 the lower portion of an upper canine corresponding in appearance to this tooth 

 as described by Professor Cope. It contained the full dentition. The decided 

 difference in the lower outline of the jaw firmly established the position of 

 Loxolophodon as an independent genus from Uintatherium. This important fossil 

 has already been described in Sillimans Journal.'^ The principal characters 

 will be repeated here. 



Since that publication the stone has been removed from another jaw of the 

 same genus which is even more complete, especially in the symphysial portion. 

 Both jaws lack the coronoid processes, nor are the condyles complete in either. 

 The teeth belonging to the former jaw are figured in Plate III., the canine, the 

 three incisors, and the complete molar-premolar series. The second, or smaller 

 jaw, has been placed in position beneath the Loxolophodon skull in Plate I. and 

 reduced in a slightly less degree than the head, as it belonged to a smaller indi- 

 vidual. 



A principal feature is the striking disproportion between the jaw and the 

 head ; this is somewhat increased by the upward and backward extension of the 

 head behind the glenoid process. This, with the absence of upper incisors, does 

 away at once with the idea that Loxolophodon had any but an herbivorous diet. 

 This question is referred to elsewhere. 



Description of the Lower Jaw. (See Plate III., Fig. i). In general contour the 

 jaw is neither long nor deep. It extends from the well-advanced glenoid cavity 

 barely to the tips of the slender premaxillaries, where it is wholly overhung 

 by the broad and projecting nasals. The coronoid process rises immediately 

 behind the last molar, projecting well up into the temporal fossa, if we can judge 

 by its stout base. The condyles, slightly above the plane of the molar series, are 

 small and decidedly convex, with their transverse axes converging. Below 

 these the posterior border narrows and then projects slightly beyond the line of 

 the condyles, roughened on the inner side for the pterygoid muscles. The lower 

 border arches gently downwards and outwards from the angle to below the 

 first premolar. Here two slight downward processes are formed, homologous 

 with the heavy pendent processes of Uintatherium, but in striking contrast with 

 the excessive development of the latter. The under surface at this point is 

 slightly concave, meeting the opposite jaw and forming a long narrow sym- 

 physis. The chin narrows into a prow-shaped keel ; it is about three and a half 

 inches long. The alveoli for the canine-incisor series converge in almost straight 

 lines, dipping downwards in front. This would throw the teeth out of the hori- 



» Vol. XVII., April, 1879, p. 304. 



