U. S. GEOLOGICAL SURVEY 



MONOGRAPH 55 PLATE CXIX 



FRONT VIEWS OF SKULLS OF ALLOPS 



Plate prepared under the direiftion of Professor Marsh. One-sixth natural size. 

 (See pp. 515, 517.) A, Allops serotinus, skuU H, coUeiftion of 1886, type (Nat. 

 Mus. 4251), South Dakota, Chadron formation, level C. The front view- 

 shows well the long, wridely divergent horns, thick nasals, and moderately 

 expanded zygomata, which are charadteri^ic of this species. B, Allops crassi' 

 cornis, skuU Z', colledlion of 1888, type (Nat. Mus. 4289), South Dakota, Chad- 

 dron formation, level lower C (in Hatcher's tabular lift of skuUs; later (1901) 

 he was "inclined to place this higher up"). In this species the horns are 

 thicker and the zygomata more massive than in A. serotinus. C, Allops sero- 

 tinus, skull Ji, referred (Nat. Mus. 4945), Big Badlands, S. Dak., Chadron 

 formation, level not lifted. The horns are more pointed at the tip than in 

 other specimens of Allops 



