478 0. C. Marsh — Horned Dinosauria. 



The resemblance in form and position of the posterior horn- 

 cores to those of some of the ungulate mammals is very strik- 

 ing, and, if detached, they would naturally be referred to that 

 group. 



The basioccipital found in place with these horn-cores, and 

 represented in plate XI (figures 1 and 2, b), is much elongated, 

 and formed the entire occipital condyle. Its exact position 

 with reference to the horn-cores could not be determined. 



Teeth, vertebrae, and limb bones which probably belong to 

 the present genus were all secured in the same horizon. They 

 indicate a close affinity with Stegosaurus, which was probably 

 the Jurassic ancestor of Ceratqps. 



Among other remains referred to the present reptile, but 

 not found with the type specimen, are some peculiar, large 

 dermal plates, in pairs, that indicate a well-ossified armor. 

 These plates show indications of being covered, in part at least, 

 with scutes, as in turtles. Their position cannot at present be 

 determined. 



The type specimen on which the present genus and species 

 are based was found in place, in the Laramie deposits of the 

 Cretaceous, in Montana, by Mr. J. B. Hatcher, of the U. S. 

 Geological Survey. Other specimens apparently pertaining 

 to the same species were secured in the same horizon of the 

 same region. 



Remains of the same reptile, or one nearly allied, had pre- 

 viously been found in Colorado, in deposits of about the same 

 age, by Mr. G. H. Eldridge, also of the IT. S. Geological Survey. 



The associated fossils found with the present specimens are 

 remains of other Dinosaurs, crocodiles, turtles, and fishes, 

 mostly of Cretaceous types. The mollusks in the same beds 

 indicate fresh water deposits. 



The fossils here described indicate a reptile of large size, 

 twenty-five or thirty feet in length, and of massive propor- 

 tions. With its horned head and peculiar dermal armor, it 

 must have presented in life a very strange appearance. 



The remains at present referred to this genus, while resem- 

 bling Stegosaurus in various important characters, appear to 

 represent a distinct and highly specialized family, that may 

 be called the Ceratopsidce. They will be described more fully 

 in a later number of this Journal. 



Yale College, New Haven, Conn., November 23, 1888. 



Explanation of Plate XI. 



Figure 1. — Horn-core and basioccipital of Ceratops montanus, Marsh; side view. 



a, born-core; 6, basioccipital. 

 Figure 2 — Horn-cores and basioccipital of same skull ; posterior view, a, left 



horn-core; b, basioccipital; c, right horn-core. 

 Both figures are one-fourth natural size. 



