PLATE CV 



Skull Related to Diploclonus tyleri 



Am. Mus. lOSl, original paratj-pe (see p. 502) of Z). bicornutus Osborn, Cheyenne River, S. Dak., Chadron formation. A', Side 

 view; A-, top view. One-fifth natural size. This skull was at first regarded by Osborn as a male of D. bicornutus, but, as 

 observed by Lull, its closer resemblances are with the tj'pe of D. tyleri. (See PI. CVII.) It approaches the type of D. amylus 

 in breadth, but the horns are not so flat. The accessory hornlets are well marked. The length of the nasals is conjectural. 

 The constricted parietal region and very concave skull top are characteristic of the menodontine group. The longitudinal 

 slit in the parietal vertex is in the region of the sagittal fossa of Manteoceras and of a parietal opening in certain skulls of 

 Brontops brachycephalus; apparently the outer tabula of the parietal bone was thin in this region. Irregular projections of 

 the temporal crest above the mid-cranial region are seen, as in Allops, and they may have marked the dorsal edge of the 

 insertion area for the temporal muscle. 



