438 THE WASATCH EPOCH. 



of the coronoid process. There are two prominent mental foramina, one 

 below the posterior border of the first premolar and one below the middle 

 of the fourth premolar. There are some less important foramina in the 

 symphyseal part of the jaw. The symphysis extends to below the poste- 

 rior border of the second premolar. 



Dentition. — The superior incisors are lost. The alveoli are nearly in 

 contact, and are round except the third, which is oval. The precanine 

 diastema is as long as the third incisive alveolus. The canine alveolus has 

 nearly twice as wide a diameter as that of the third incisor. The section 

 of the crown is subtriangular, the anterior face wearing flat. The first 

 premolar is situated near to the canine, and the single alveolus is a little 

 larger than that of an incisor. The crown is lost. The second premolar is 

 two-rooted. The crown is longer than wide or high, and consists of a single 

 angular cusp. The external face is flat, and the internal face is convex. 

 The base of the crown widens posteriorly, but does not produce a heel, as 

 its surface is everywhere a steep continuation of the inner face. No ante- 

 lior basal tubercle. The base of the third premolar is triangular in form, 

 the base being posterior. The external elevation has a triangular outline, 

 but the posterior edge is interrupted by a secondary cusp less elevated than 

 the principal one. The internal cusp is opposite this posterior one, and 

 is not quite so elevated. Its base projects well inwards. No cingulum 

 excejjt at the anterior base. The fourth premolar has a subquadrate out- 

 line, the internal angles being rounded off". The two external cusps are 

 subequal in elevation, and they are only distinguished externally by a short 

 gi'oove, which does not extend to the base of the crown. The general ex- 

 ternal surface is nearly flat There is an anterior intermediate tubercle, but 

 no posterior one. No transverse crests. 



The outlines of the true molars are obliquely subquadrate, the last 

 molar being the most oblique. Their external tubercles are round at the 

 base, l)ut somewhat flattened at the apex. The internal tubercles are 

 rounded on the inner, and flattened on the outer side. The inttTUKMliate 

 tubercles are distinct from both. There is a narrow cingulum interrupted 

 at jjoints. It rises into a weak anterior external angle, and a strong tubercle 

 at the notch which separates the external tubercles. On the last molar the 



