1898.] Wort/nan, Extinct Camelidie of North America. 121 



retained in the jaw for a longer or shorter period, and in some 

 instances until the animal was almost if not quite adult. ' In view 

 of these facts I am disposed to interpret this specimen as a case 

 of abnormal retention of the incisors of the rather abundant 

 species P. robiistus. If this conclusion is correct, then the spe- 

 cies Protolabis heterodontus becomes a synonym of Procamelus 

 robiistus. The second species regarded as belonging to this genus 

 from the Nebraska Loup Fork, Protolabis prehensilis Cope, was 

 founded upon the anterior portion of a lower jaw without teetli, 

 and as there is no indication whatever what the upper dentition 

 was like, the reference at most is mere guesswork. In fact, I 

 doubt very much if it even is specifically distinct from Proca- 

 melus robiistus. 



With the elimination of these forms from the Nebraska Loup 

 Fork, we have left tlie single species Protolabis tra/ismontanus, 

 represented by the Oregon specimen above referred to. In this 

 specimen we have a genuine case of normal retention of the supe- 

 rior incisors, a fact which separates it at once from Procamelus, 

 but the distinctions between it and its predecessor, Gompliotlic- 

 rium, are less clear. Cope assumed that it differed from this 

 latter genus, in the coossification of the metapodials into a can- 

 non bone, but of this there are no specimens at present known to 

 demonstrate the truth or falsity of such an assumption. It is true 

 that Camel remains have been found in the Deep River Beds of 

 Smith's Valley, Montana, which deposits have been generally 

 looked upon as older than the Loup Fork of both Oregon and 

 Nebraska. These fossils have been uniformly referred to the 

 genus Protolabis by Cope and Scott, but it does not appear, from 

 any materials with which 1 am acquainted, whether these remains 

 have been correctly determined or not. Neither skulls, jaws, nor 

 even teeth, are known from this horizon which would enable one 

 to say definitely whether the dentition was that of Protolabis or 

 Procamelus. The metapodials of both fore and hind feet are 

 united into a cannon bone, and the size almost, if not quite, 

 equals that c)f Procameiiis robiistus, a circumstance which would 

 seem to indicate that if they belong to the genus Protolabis they 

 must represent a different and later species, since Protolabis 

 traiisuiontanus is much smaller, scarcely exceeding Gomphotherium 



