DYSGANUS. 67 



Canadian Geological Survey, chiefly through the efforts of the vertebrate paleontologist, Mr. 

 Lawrence M. Lambe. The more recently collected materials of the American Museum of 

 Natural History in New York, of the Carnegie Museum at Pittsburg, the Museum of the University 

 of Chicago, and the Museum of the State University of Kansas have also been freely placed at 

 the disposal of the writer. 



The earlier, smaller, more primitive, and less specialized mid-Cretaceous forms from the 

 Judith River and Belly River beds will be first considered, followed by a description of the 

 larger and more specialized forms from the later Laramie deposits of Converse County and 

 Black Buttes, Wyoming, and from the Denver beds of Colorado, which latter have been consid- 

 ered by some as of post-Laramie age. 



REVISION OF SPECIES OP JUDITH RIVER CERATOPSIA. 



GENERA AND SPECIES DESCRIBED BY PROFESSOR COPE. 



DYSGANUS Cope. 1876. 



Type species, D. encaustus. 



Original description in Proc. Acad. Nat. Sci. Phila., vol. 28, 1876, p. 250. 

 Cope, E. D., Bull. U. S. Geol. and Geog. Surv. Terr., vol. 3, 1877, pp. 572, 596; Proc. Acad. Nat. Sci. Phila., 1883, p. 99; Am. 



Nat., vol. 24, 1890, p. 571. 

 Nopcsa, F. Baron, Foldtani Kozlony, Budapest, 1901, vol. 31, p. 270. 

 Osborn, H. F., Contr. Canadian Pal, vol. 3 (quarto), pt. 2, 1902, p. 20. 



This genus was proposed by Professor Cope in 1876, when he also gave brief descriptions 

 of four supposedly new species (D. encaustus, haydenianus , bicarinatus, and peiganus) which he 

 considered as pertaining to it. Neither in his original nor in any subsequent description did 

 Cope state definitely what he considered the affinities of the representatives of this genus. Hay, 

 in his Bibliography and Catalogue of the Fossil Vertebrata of North America, has placed this 

 genus in the Trachodontidse, while Nopcsa, in his Synopsis und Abstammung der Dinosaurier, 

 has considered it as pertaining to the Ceratopsidae. Since the specimens upon which was 

 based the type species of the genus and the types of any of the other species are no longer deter- 

 minable a in the Cope collection, we have now to rely entirely upon his descriptions for the deter- 

 mination of those characters which might throw light upon the question of the relationship of 

 this genus. Before discussing it further, therefore, it would seem advisable to quote in full 

 Professor Cope's original description of the genus and its several species. 



Dysganus encaustus Cope, 1876. 



Type (No. 5739, American Museum of Natural History) consists of,detached teeth. 



Original description in Proc. Acad. Nat. Sci. Phila., vol. 28, 1876, pp. 250-251. 

 Cope, Bull. U. S. Geol. and Geog. Surv. Terr., vol. 3, 1877, p. 572. 

 Nopcsa, F. Baron, Foldtani Kozlony, Budapest, 1901, vol. 31, p. 270. 

 Osborn, H. F., Contr. Canadian Pal., vol. 3 (quarto), pt. 2, p. 14. 



Char. gen. — A large number of teeth exhibit the characters of this genus, which is a peculiar form of herbivorous Dino- 

 sauria. The crowns are compressed so that the fore-and-aft diameter much exceeds the transverse. The body of the crown 

 is a flattened shaft of dentine, one face of which is the denser and produces the cutting edge. This face is flat or weakly 

 keeled, while there are two other faces uniting at an open angle, thus giving a subtriangular section. On each of these faces 

 is adherent a shaft of cementum-like material of a dense character, whose external face is longitudinally concave. These 

 inclose between them on the median line a deep groove, which expands below into a wide concavity, which appears to be 

 enlarged as the age of the tooth increases preparatory to shedding. The other parts of the base of the crown below the cutting 

 face are inclosed in a father thick deposit of rugose cementum, which rises a distance on the sides of the tooth. 



The method of replacement of the teeth in this genus appears to resemble that of Cionodon, except that there is no 

 indication of the existence of as many series in the transverse direction. The longitudinal grooves in the anterior and pos- 

 terior cement columns are probably occupied by the borders of the apices of successional teeth. The presence of these columns, 

 etc., distinguishes this genus from that and other allied genera. 



Char, specif. — The cutting face, is more or less concave and is impressed or sunken, its lateral borders and the cement 

 of the basis projecting beyond it. The inferior border is also usually oblique, that of one of the sides rising diagonally. In 

 the same proportion a weak keel is also unsymmetrically placed, lying close to the opposite border and dividing the face into a 

 wide and a narrow concavity. The oblique border is also incurved, the edge of the posterior cement column curving round 



a All types of Ceratopsia in the American Museum of Natural History, except that of Agathaumas milo, have now been identified.— R. S. L. 



