1898.] IVort/naii, Extinct Cainelidce of A^orth America. I 15 



In many of the later Camelidse. In Poebrotheriufn again, the 

 orbit is not inclosed by bone posteriorly, whereas in Gompho- 

 tJieriiiin the {posterior boundary of the orbit is com])lete. Another 

 important distinction is seen in the character of the articular 

 facets of the third and fourth metapodials of the fore foot. In 

 Poclr? otheriinii these bones give evidence of having been more 

 widely separated in the living animal, and capable of consider- 

 able independent movement, the facets being relatively large 

 and tlie opposed surfaces comparatively smooth. In Gomp/io- 

 theriiim these facets are much reduced, the metapodials closely 

 applied to each other and their contiguous surfaces much rough- 

 ened, clearly foreshadowing the coossification of these elements 

 into a cannon bone. 



Gomphotherium Sternberg! Cope. 



The type of this species consists of the greater part uf the 

 skeleton of a single individual in good preservation from the 

 lower beds of the John Day Valley, Oregon. Other specimens 

 from the same horizon include more or less perfect foot-bones, 

 fragments of jaws, and other parts of the skeleton. The form of 

 the skull presents a striking resemblance to that of the modern 

 Camels in its general make up. The nasal bones are, however, 

 proportionately longer, the bony roof of the orbits not so broad, 

 and the muzzle apparently more laterally constricted in front of 

 the infraorbital foramen. As compared with Poebrothcriiim and 

 the Llama the face is less bent down on the basicranial axis, in 

 this respect resembling more the skull of the Camel. The verti- 

 cal depth of the face immediately in front of the orbit is rela- 

 tively greater than in Poebrotheriuiii., and the opening of the 

 posterior nares has a more forward position. 



A very interesting transition from the relatively low, much- 

 swollen otic bullee of PocbrotJicriiim, to the high, little-swollen 

 condition of these parts in the living species, is observable. The 

 otic bullae of all the Camels are highly characteristic ; they con- 

 sist of an inner, longitudinally-directed swollen part, together 

 with an outer vertical buttress, which joins the inner part at an 

 angle, and at the upper limit of which is j^laced the external 



