ORDER VIII 



DINOSAURIA 



245 



with three hoofed digits. Dermal armour not observed. Laramie Formation ; 

 Montana, Wyoming, and Colorado. 



Cent fops (Monoclonius, Cope), Sterrholophus (Fig. 351), Torosaurus, Marsh. 



Fig. 351. 



SterrholopTvus flabellaius, Marsh. Uppermost Cretaceous ; Montana. Lateral and superior aspects of skull, 

 !/o . A, Orbit; e, Marginal bosses (" epioccipital plates"); /, Brain; h, Horn-core ; h', Nasal lmrn-core ; .V. 

 External narial opening; n, Xasal ; p, Parietal; pd, Predentary (restored in outline); q, Quadrate; r, Rostral 

 bone (restored in outline) ; S, Supratemporal vacuity ; s, Squamosal (after Marsh). 



These are less perfectly known, but apparently allied genera accompanying 

 the preceding in the Laramie Formation. 



Range and Distribution of the Dinosauria. 



The remarkable and by no means homogeneous group of Dinosauria arose 

 during the Trias, attained its maximum development in the Upper Jura and 

 Cretaceous, and passed entirely away at the close of the latter period. The 

 abundance of Dinosaurs during the Trias is indicated by countless footprints 

 in the sandstones of that age in Massachusetts, Connecticut, Pennsylvania, 

 Virginia, and North Carolina, where hordes of these creatures roamed along 

 the beaches in quest of prey. Upwards of 100 different varieties of footprints 



