DISCOVERY OF THE TITANOTHERES AND ORIGINAL DESCRIPTIONS 



239 



Type. — "A robust, short left mandibular ramus," 

 lacking the posterior end. The three molars and the 



the fourth premolar and the first molar. The bone is massive 

 and heavy throughout. The mental foramen is placed beneath 

 the posterior root of the third premolar, farther back than in 

 M. ■primiiivus. 



The cingula are very slightly developed. The external cingu- 

 lum is present for a short distance only, on the anterior face 

 of each of the four teeth, and in the third molar in advance of 

 the heel. The only trace of an internal cingulum is to be seen 

 in the third molar on the posterior slope of the heel. 



Figure 204. — Type (holotype) jaw of Megacerops primiiivus 

 In the collection or the Ottawa Museum. After Lambe, 1908. A, Superior aspect, one-half natural size; B, lateral aspect, one-third natural size. 



fourth premolar are preserved, as well as part of the 

 symphyseal region. Ottawa Museum. (See fig. 205.) 



The fourth premolar is fully molariform. The teeth are 

 stout and of about the size of the corresponding ones in M. 



Figure 205. — Type (holotype) jaw of Megacerops assiniboiensis 

 In the collection of the Ottawa Museum. After Lambe, 1908. One-third natural size. 



Characters. — Lambe writes: 



The jaw is much deeper, thicker, and relatively shorter than 

 in angustigenis and primiiivus, and the teeth are much larger 

 than in these species. It is narrow anteriorly, and the sym- 

 physis extends back to a point in line with the division between 



marshi Osborn, but the jaw is relatively shorter than in this 

 species. 



From the material available, the species, for which the 

 provisional name assiniboiensis is proposed, can not be defi- 

 nitely characterized. 



