502 0. C. Marsh — Skull of the Gigantic Ceratopsidai. 



The fossils associated with the OeratopndcB are mainly 

 Dinosaurs, representing two or three orders, and several families. 

 Piesiosaurs, crocodiles and turtles of Cretaceous types, and 

 many smaller reptiles, have left their remains in the same 

 deposits. Numerous small mammals, also of ancient types, 

 a few birds, and many fishes, are likewise entombed in this 

 formation. Invertebrate fossils and plants are not uncommon 

 in the same horizon. 



The Ceratopsidce, as the most important of this assemblage, 

 will be first described fully by the writer, under the auspices 

 of the United States Geological Survey. In the present paper, 

 the skull of one of these gigantic reptiles is briefly described, 

 and figured, as a typical example of the group. 



The Skull. 



The skull of Triceratojps, the best known genus of the 

 family, has many remarkable features. First of all, its size, in 

 the largest individuals, exceeds that of any land-animal, living 

 or extinct, hitherto discovered, and is only surpassed by that of 

 some of the Cetaceans. The skull represented in Plate XII, 

 the type of the species, is that of a comparatively young animal, 

 but is about six feet in length. The type of Triceratops 

 horridus was fully adult, and probably an old individual. 

 The skull, when complete, must have been over eight feet in 

 length. Two other skulls, both nearly perfect, now under 

 examination by the writer, fully equal in bulk the two already 

 described, and other similar specimens from the same horizon 

 maintain equal average dimensions. 



Another striking feature in the skull of this genus is its 

 armature. This consisted of a sharp cutting beak in front, a 

 strong horn on the nose, a pair of very large pointed horns on 

 the top of the head, and a row of sharp projections around the 

 margin of the posterior crest. All these had a horny covering 

 of great strength and power. For offense or defense, they 

 formed together an armor for the head as complete as any 

 known. This armature dominated the skull, and in a great 

 measure determined its form and structure. 



The skull itself is wedge-shaped in form, especially when 

 seen from above. The facial portion is very narrow, and much 

 prolonged in front, as shown in Plate XII, figure 2. In the 

 frontal region, the skull is massive, and greatly strengthened 

 to support the large and lofty horn-cores, which formed the 

 central feature of the armature. The huge, expanded parietal 

 crest, which overshadowed the back of the skull and neck, 

 was evidently of secondary growth, a practical necessity for 

 the attachment of the powerful ligaments and muscles that 

 supported the head. 



