124 THE CERATOPSIA 



This is one of the largest Triceratops skulls on record, having an over-all length of 6 feet 

 10^4 inches, in spite of its being not fully adult. The disproportionately long muzzle increases 

 the length over that of elatus which, otherwise, it resembles most closely. The dorsal profile is 

 very comparable to that of elatus, as superimposed outlines would show. The imperfection of the 

 median portion of the crest in the present specimen makes the comparison of this region of less 

 value, however. 



The orbit is an elongated ellipse, slightly broader above and, as in elatus, inclined at an angle 

 of about 15° from the perpendicular. The jugal is of medium width, and tapers to a point in the 

 distal half. It differs from that of elatus in having the usual rear branch above, and is, therefore, 

 T-shaped rather than in the form of an inverted L. But that of elatus may be abnormal, and were 

 that of the opposite side preserved, it might be found to resemble that of calicornis. There is a 

 slight longitudinal ridge on the jugal about two-thirds of the way toward the rear of the bone. 

 The jugal notch is of moderate depth, but is wide, with curved outline. 



The infratemporal fossa is rather small for the size of the skull and differs, not only in this, 

 but also in shape, from that of elatus, being oval in form, with a rather long apex pointing downward 

 and forward. The muzzle is very long, more like that of Chasmosaurus than Triceratops. The 

 face is also long. In this respect, calicornis differs from Chasmosaurus in which, despite the fact 

 that the muzzle is long, the face is very short. The narial opening in calicornis is very large, in 

 correspondence with the large muzzle. The rostral is also large, with a very convex profile. The 

 downwardly curving inferior margin is rather sharp-edged. 



The nasal horn is very peculiar, and here, as in prorsus, it was the most distinctive feature in 

 the eyes of Professor Marsh, who gave the name calicornis to the species because the rear of this 

 small nasal horn resembled a horse's hoof as seen from below. As in elatus, the dorsal margin of 

 the horn core is not continuous with, but below that of the nasal bones, the horn being thus sharply 

 marked off from the nasals. The horn is convex in front and concave behind, hence the hoof-like 

 form. There are vascular impressions on the rounded anterior surface. Viewed laterally, the horn 

 has a pointed apex. The horn of both the elatus type and of the skull No. 2100 U.S.N. M., on the 

 mounted skeleton at Washington, are of the same general character, although the hollowed rear 

 surface is peculiar to the present specimen. 



The brow horns are large, agreeing with those of elatus in size, massiveness, and general curva- 

 ture, and in the possession of a boss-like prominence on the rear of the base. They have a very 

 heavy base from which they taper rapidly, curving sharply forward but without the reversed curve 

 toward their tip. 



The crest is only partially preserved, the entire left squamosal and about a third of the median 

 element only being present. The left squamosal is about twice as long as broad, with a uniformly 

 curved, rather than undulating, margin. Otherwise, the margin is smooth and rather thin. There 

 were probably the usual number of epoccipitals, perhaps 19 in all, although but two are preserved. 

 A few shallow vascular impressions are present on the upper surface of the crest. Below, they are 

 deeper, especially in the posterior part of the squamosal, and extend further in from the margin, 

 there being no limited zone of vascular grooves such as that of prorsus, brevicornus, and the skull 

 No. 2100 U.S.N. M. The crest is unusually wide when viewed from above, being over twice as 

 wide as long, according to Hatcher's figure. 80 The pseudopineal fontanelle is present, and large, 

 but the radiating canals, if they formerly existed, are not preserved. The preorbital fossa lies 

 between the nasal and maxillary, and is reduced to a rather wide, elongated slit. 



The dentaries are of great size; otherwise, according to Gilmore, 81 they show no distinctive 

 characters. There are 38 rows of teeth in the left dentary, opposed to 28-32 in the maxillary, the 

 exact number being difficult to determine. If this is the lower jaw actually belonging to the skull, 

 it is difficult to account for this discrepancy, for no fore and aft or orthal movement of the mandible 

 was possible. Microscopic striae of wear on the worn surface of the teeth prove vertical movement 

 only. 



80 Hatcher, Marsh, Lull, 1907, PL XXXIX. 



81 Gilmore, C. W., 1919, B, p. 101. 



