TRICERATOPS PEOESUS. 127 



Mm. 



Distance from anterior border of orbit to posterior border of nasal opening. 266 



Distance between orbit and lateral temporal foramen. _ 145 



Distance between lateral and supratemporal foramina 2.59 



Distance from lateral temporal foramen to posterior extremity of squamosal 780 



Circumference of supraorbital horn core at base. . . 490 



Circumference of supraorbital horn core 200 mm. above base 345 



Triceratops prorsus Marsh. 1890. 



Type consists of nearly perfect skull with lower jaw (No. 1822, Yale Museum), Laramie of Converse County, Wyo. 



Original description in Am. Jour. Sci., vol. 39, Jan., 1890, p. 82. 

 Marsh, O. C, Am. Jour. Sci., 3d ser., vol. 41, Feb., 1891, pp. 177-178: Apr., 1891. pp. 339 and 342: vol. 43, Jan., 1892, 



p. 84; Nature, vol. 48, Sept. 7, 1893, p. 337; Am. Jour. Sci., 3d ser., vol. 48, July, 1894, p. 90; Mon. U. S. Geol. Survey, 



vol. 27, 1897, p. 516; Sixteenth Ann. Kept. U. S. Geol. Survey, 1896, pt. 1, pp. 218. 

 Dana, J. D., Manual of Geology, 1895, p. 846. 



Fiirbringer, M., Zeitschrift fur Naturwissen., Jena, 1900, vol. 34, p. 351. 

 Hutchinson, H. N., Extinct Monsters, 1893, p. 116. 

 Lambe, L. M., Contr. Canadian Pal., vol. 3 (quarto), pt. 2, 1902, p. 60. 

 Lydekker, R., Some Recent Restorations of Dinosaurs, Nature, vol. 48, 1893, p. 304. 

 Nopcsa, F. Baron, Foldtani Kozlony, Budapest, 1901, vol. 31, p. 271. 



Osborn, H. F., Science, new series, vol. 7, 1898, p. 844; Contr. Canadian Pal., vol. 3 (quaito), pt. 2, 1902, p. 14. 

 Woodward, A. S., Outlines Vert. Pal., p. 213, 216. 

 Zittel, K. A. von, Text-book Pal., trans, by C. R. Eastman/vol. 2, p. 244. 



ORIGINAL DESCRIPTION. 



The present species was based on a nearly complete skull (No. 1822, Yale Museum) , with, 

 lower jaw and the six anterior cervicals of an individual fully adult. Marsh's original description 

 of this species was as follows : 



A second skull of this genus, fully adult, and of nearly equal dimensions, was secured at the same time as the specimen 

 last described. It is in excellent preservation, although somewhat distorted, and evidently belongs to a different species. 



The nasal horn core and the rostral bone are in position, and perfect. The former is very large and is directed straight 

 forward, its upper surface being nearly on a line with the superior face of the nasals. It is somewhat oval in transverse 

 section, and pointed in front, the apex being directly above the anterior extremity of the rostral bone. It is so firmly 

 coossified with the nasals that no trace of a suture can be observed. Its external surface is rugose from vascular impressions, 

 indicating that it was covered by horn, thus forming a most powerful weapon. 



The huge frontal horn cores are more massive and less slender than in the species above described. 



The parietal crest is not so broad as in the two species last described, but appeal's to resemble more closely that of 

 Triceratops horridus, its sides being inclined downward, as if to protect the neck. 



The rostral bone likewise is very similar to that in the last species, but is somewhat more compressed. The two forms 

 may be readily distinguished by the nasal horn core, for in T. horridus this is comparatively small and points directly 

 upward, instead of straight forward, as in the present species. 



With this skull were found several cervical vertebrae and some other portions of the skeleton. The atlas, axis, and 

 the third vertebra are firmly anchylosed with each other, and their ribs, also, are coossified in the same mass. This union, 

 unknown hitherto among the Dinosauria, was evidently rendered necessary to afford a firm support for the enormous skull. 

 The remaining cervical vertebra; are short and massive, and the articular faces of the centra are concave or nearly flat. 



The present specimen is from the Laramie of Wyoming, and was found in the same vicinity as the skull above described. 



LOCALITY. 



The type of the present species, as already stated, consisted of the skull, lower jaw, and the 

 six [seven] anterior cervical vertebrae (No. 1822, Yale Museum). They were found by me on July 

 4, 1889, incased in a hard concretion of calcareous sandstone, which had nearly weathered 

 out of a thick stratum of rather soft and almost white sandstone. The locality, shown at 

 + 3 in PL LI, was situated about 100 yards above and on the same side of the canyon as 

 that at which the type of the species last described was obtained. When discovered, the 

 skull lay a few feet above the bottom of the canyon and at a slightly lower horizon than the 

 type of T. serratus. Between the position occupied by these two skulls on the opposite 

 side of the canyon there extends for a distance of perhaps 200 feet a perpendicular wall, 

 perhaps 20 feet in height, near the summit of which, at the point marked O B sp., PI. LI, 



