536 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



760 millimeters, nasals to top of occiput 695, width 

 across zygomata 555, zygomatic index 73 (that is, sub- 

 brachycephalic). Nasals decidedly shorter than in 

 M. giganteus (free length 105 mm., breadth 140). 

 The horns are outwardly directed but of similar section 

 to those in M. giganteus. Two vestigial upper inci- 

 sors retained on each side. Premolar-molar series 

 (410 mm.) relatively very long (dental index 54). 

 Premolar tetartocones very distinct. P* with redupli- 

 cate tetartocone. Hypocone on m' large and distinct 

 from the cingulum. 



This animal appears to be specifically distinct from 

 M. giganteus and to present a form which tends to 

 bridge over the structural gap between Menodus and 

 Allops, since while exhibiting all other characters of 



the protocone and the hypocone of m^ being well worn. 

 In its superior aspect the skull is very similar to 

 Marsh's type of ingens, although less dolichocephalic; 

 the horns are connected by the characteristic low trans- 

 verse crest. In the plane of the posterior faces they 

 are crushed downward and outward in such a manner 

 as not only to change their normal elevation but to 

 decrease the acuteness of the trihedral section and 



Figure 446. — Lower Jaws of Menodus giganteus 



A, Am. Mus. 500, ? (cf. flg. 445); B, Field Mus. P 5927, a large male. Both jaws have the ramus elongate, the 

 into a rounded elbow, and the teeth sharply cingulate. One-fifth natural size. 



ngle produced posteriorly 



M. giganteus, it possesses the short nasals character- 

 istic of Allops. That this skull may be an Allops is 

 further indicated by its sub-brachycephaly (index 73) 

 as in Allops serotinus, also by the proportions of its 

 horns and nasals. 



Materials. — The species is known only from the 

 type skull in the Yale Museum (No. 12060), which is 

 represented in Plate CXLII. 



Description oj the type. — The type skull is that of an 

 old animal in the eighth to ninth stage of growth, both 



make it difficult to express in cross section (fig. 444, C) 

 their actual form. The nasals had the spread but not 

 the length characteristic of Menodus. In inferior 

 aspect of the skull the nares open immediately behind 

 the second molar, as in M. ingens. There are traces 

 of a median vomerine keel and a very prominent 

 rugose projection at the junction of the basisphenoid 

 and basioccipital, which is apparently broken away in 

 the type of M. ingens. As in M. ingens the orbit is 

 directly above the posterior portion of the first molar. 



