282 F.'B. Loomis — On Ticholeptus Rusticus and 



sired in determining the position of an oreodont. This 

 skull of Cope's is less like the one I have than are the two 

 of Douglass's descriptions, but the four (and perhaps T. 

 bannockensis) make a very uniform group completely sep- 

 arated from the other oreodonts by having hypsodont 

 dentition, medium length limbs, skulls with light zygo- 

 matic arches, and antorbital fenestra of considerable size. 

 As oreodonts are classified with reference to the whole 

 skeleton perhaps more than any other great group it is 

 essential that as rapidly as possible we should have more 

 figures of the whole skull or better of the whole skeleton. 

 This material is generally abundant in the various 

 museums and it is desirable that for every species a com- 

 plete skeleton should be described. The following is an 

 outline of all that I can get in regard to Ticholeptus rusti- 

 cus. 



Ticholeptus rusticus Leidy. 



Merycochcerus rusticus Leidy, 1870, Proc. Acad. Nat. Sci., 

 Philad., p. 109. 



Merycochcerus rusticus Leidy, 1873, Rep. U. S. Geol. Surv. 

 Territories, p. 199, fig. 1-5, PL 17. 



Merycochcerus rusticus Matthew, 1901, Hem. Amer. Museum 

 Nat. Hist., vol. 1, p. 412 and figs. 



In this species the skull is lightly built throughout, and 

 moderately elongate, more so than in either T. brachy- 

 melis or T. breviceps. The orbit is set well back, its pos- 

 terior margin being a little behind the back of the last 

 molar, while in T. brachymelis it is over the back of this 

 tooth, and in T. breviceps it is still further forward. The 

 whole brain case is longer in this species than the others 

 mentioned. The nasal bones are considerably shortened, 

 ending just over premolar 3, while those of T. brachy- 

 melis and T. breviceps end over premolar 1. In all these 

 this is an unusually short nasal, but not of the character 

 of M. proprius so that it does not suggest the development 

 of a proboscis as in that genus, but I would take it rather 

 as indicating a snout more like that of modern pigs. Cor- 

 related with the shortening of the nasals is the position of 

 the infraorbital foramen which in this species is just over 

 the contact of premolar 4 and molar 1, while in the other 

 two species it is further forward by the width of the 

 fourth premolar. There is a large prelacrymal fenester 

 situated rather far forward on account of the extension 



