DAKOTA AND NEBRASKA. 143 



an angularly bent ridge or laclir;^Tnal process, within the position of which there is 

 situated the orifice of the lachrymo-nasal duct. 



The only parts visible of the base of the cranium are the auditory bullte, which 

 appear of enormous size. They extend nearly half the depth of the back part of the 

 lower jaw, reach outwardly several lines beyond the general plane of the external 

 surface of the latter, and' internally are within five lines of each other. Postero- 

 internally they abutted against the paramastoids, and auterioi'ly they project within 

 the position of the lower' jaw. They are about an inch in breadth fore-and-aft, three- 

 fourths of an inch in thickness behind, and about eleven lines in length. Their 

 inner surface is nearly flat and parallel; their outer surface is more convex, and 

 directed forward. They are most convex and narrowest anteriorly, are thick and 

 convex beneath, and are prominently convex postero-externally. Their back part 

 appears doubled so as to enclose a vertical gutter ending below in a pit, with a 

 process for the conjunction of the styloid bone. 



The external auditory meatus has the appearance of a small loop, suspending the 

 auditory bulla like a bag behind the glenoid articulation. In its present condition in 

 the fossil, which, however, appears to he perfect, it is very short and does not reach 

 outwardly within a couple of lines of the external prominence of the auditory bulla. 

 It opens outwardly with a feeble inclination downward and backward. 



The lower jaw approaches near-est in form that of the Camel among living 

 ruminants. The base is nearly horizontal as in the Camel, but is rather more 

 flexuose. The downward convex production of the extremities and middle nearly 

 reach the same plane. The alveolar border at the back part makes a steep do'mi- 

 ward and forward sweep, but rises again from the position of the fiirst true molar to 

 the beginning of the closed row of molars, when it again descends along the hiatus to 

 the first premolar. 



The body of the lower jaw is thickest and most convex at the middle, and most 

 vertical at the back part and below the premolars. The posterior portion of the jaw 

 extending from the alveolar border obliquely backward and downward is of great 

 comjDarative breadth. The posterior border forms a hook-like process as in the 

 Camel family. The end of the hook is just below the middle of the depth of the 

 jaw from the condyle. The margin below is convex and continuous with the base 

 of the bone. The margin above forms a semi-circle, occupied by the outwardly 

 projecting portion of the auditory bulla. 



The condyle, so far as it is visible, appeal's to resemble that of the Lama. The 

 coronoid process rises nearly as in the latter, but appears not to have l^cen so long. 

 Below the process externally there is a comparative!}^ deep fossa, as in tlie Nioljrara 

 genus Procamelus. 



