PLATE CXLVI 



Skulls of Megacehops acer 

 Side view. One-fourtia natural size. (See p. 545) 



A, Type (Am. Mus. 6348) , Horsetail Creek, northeastern Colorado, Chadron formation. A more perfect skull of this species is 



shown in Figure 452, p. 548. Horns elongate, subcylindrical in basal section, with low connecting crest. Affinity with 

 Bro?itotkerium seen in general configuration of nasals, horns, and cranium. 



B, Referred female skull (Am. Mus. 6350; type of Symhorodon altirostris Cope), Horsetail Creek, northeastern Colorado, Chadron 



formation. Regarded by Osborn as a female of M. acer, but the specific reference is uncertain. The basal section of the 

 horns and the general configuration of the skull are similar to M. acer, but the nasals are shorter; the horns are also short and 

 without connecting crest. The front view (PL CL, B) shows well the high position of the nasals {"altirostris"), the alveoli 

 for two small incisors, the large, rounded opening of the infraorbital canal. Affinity with the supposed female of M. bucco 

 (figured in PI. CXLV) is indicated, especially in the top view (PI. CXLVIII) and in the palate (PI. CL; compare PI. CLII). 



