188 THE CERATOPSIA. 



Agathaumas, from the lower Laramie, is known only from certain portions of the skeleton 

 and seems to be transitional between Monoclonius and Triceratops, while Triceratops alticornis, 

 from the Denver beds and therefore the most recent of all, exhibits a type of supraorbital horn 

 core which may readily be considered the final stage in the evolution of these weapons. 



In the table of stratigraphical sequence (p. 184) the relative positions of the various type 

 specimens are given, except where the level is unrecorded. The phylogenetic series corresponds 

 approximately with the stratigraphic sequence, although of the two Torosaurus species Hatcher 

 distinctly states that gladius ' ' represents the extreme development of that type of parietal pecu- 

 liar to this genus," thereby implying that T. gladius, which is geologically the older, is the 

 more specialized of the two. 



PROBABLE APPEARANCE OF THE CERATOPSIA. 

 THE JUDITH RIVER TYPES. 



Our knowledge of the general form of the earlier Ceratopsia is still very vague, for with the 

 exception of Monoclonius crassus, among Judith River types, most of the remains are of incom- 

 plete skulls only. 



But two attempts have been made to restore Judith River forms, consisting of a statuette 

 and a painting, both by Charles R. Knight. The restorations, which differ somewhat from 

 each other, have been called Agathaumas sphenocerus, the supposition being that Monoclonius 

 and Agathaumas were synonymous genera, the latter term having priority. The restoration 

 is really that of Monoclonius sphenocerus Cope. 



The statuette, the property of the American Museum of Natural History, is figured as 

 PI. I, fig. 1, in the Catalogue of casts, models, photographs and restorations of fossil vertebrates, 

 by Professor Osborn/ 1898. The painting, also in the American Museum, was reproduced in 

 the Century Magazine 6 for November, 1897. 



The conception of the tall, straight nasal horn and the much smaller supraorbital horns is 

 undoubtedly correct, though in Monoclonius sphenocerus the compressed nasal horn slants some- 

 what backward, while in other species of the genus it curves to the rear. The writer questions 

 whether the hinder margin of the frill was quite so prominent as it is represented in the model 

 and painting, for in the earlier types the whole crest is much less strongly developed than in the 

 later forms, and although the edge is crenulated yet there is little reason to suppose that the 

 marginal armature was as well developed as it appears to be in the restoration. The general 

 bodily proportions are based upon "a reconstruction of a possibly identical and prior restoration 

 of Triceratops prorsus (Marsh)" (Ballou). It is now known that Marsh was in error in making 

 the presacral series of vertebrae too numerous in his restoration of Triceratops (fig. 125), hence 

 the probabilities are that here again the back is unduly elongated, though of this we have no 

 positive knowledge. 



The Judith River Ceratopsia were smaller than their Laramie successors, and of lighter and 

 less muscular build, and from the development of cranial armature differed in their offensive 

 and defensive tactics. 



It is difficult to conjecture in what way Oeratops would differ in external appearance from 

 its contemporary Monoclonius except in the much greater development of the supraorbital 

 horns. The nasal horn core is unknown except in one species, Oeratops (Monoclonius) recurvi- 

 cornis Cope, in which it curves strongly forward, in contrast to that of Monoclonius. As this 

 species differs from the others that Hatcher refers to Oeratops in an important anatomical 

 feature — namely, in the presence of separately ossified epoccipital bones — the present writer 

 is loth to consider it as typical of the genus, if, indeed, it belongs with Oeratops at all. 



There are no data concerning the bodily proportions or contour of Oeratops. 



n See also Science, vol. 7, p. 842, fig. 1. i Ballou, W. H., Strange Creatures of the Past, p. 18. 



