220 THE CERATOPSIA 



over-all length is about the same. A similar cause may have given rise to a difference in inclination 

 of the hinder margin of the nasal septum, which is more erect in the type. The brow horns are 

 relatively shorter in the Carnegie Museum specimen, compared with the over-all length of the skull, 

 and taper more uniformly, without the abrupt, somewhat truncated appearance of the type. Their 

 curvature corresponds so far as the mass of the horn is concerned, but not in the anterior margin. 

 The orbits are similar in shape and inclination, but those of the larger skull are relatively smaller. 

 The jugals are alike, except that in the Carnegie skull they have a somewhat greater fore and aft 

 diameter. The jugal notch is wider, owing to a gentler marginal curve at the anterior end of the 

 squamosal. The infratemporal fossa is smaller and more ovoid than in the type. The crest is 

 similar in general proportions but the dorsal profile is less undulatory, and the curve rather more 

 abrupt at mid-length. The mandible, rostral, and predentaries agree. This skull is without doubt 

 referable to brevkornus, the differences being such as are included under individual and possibly 

 sexual, but not age variation. 



Triceratops serratus Marsh 70 



Holotype: 71 No. 1823 Y.P.M.; nearly perfect skull with lower jaw. 

 Horizon: Lance formation, No. 18 in the sequence. 

 Locality: Niobrara County, Wyoming. 

 Collector: C. E. Beecher, 1889. 



This type consists of a magnificently preserved skull, jaws, and hyoid, but no other skeletal 

 material. The skull is fairly large— 5 feet 1 1 inches— although below the average; but as the 

 animal was immature, it might have attained average proportions had it lived. The muzzle and 

 face are long, and the profile of the face and crest are in line with each other. The facial profile 

 is first slightly concave, then convex, forming a reversed curve, differing therein from the simple 

 curve, concave upward, found in every other species but obtusus. The orbit is a broad ellipse, with 

 the long axis inclined as usual some 45° from the perpendicular. The descending limb of the jugal 

 is narrow, parallel-sided for about half its length, then, after a slight dilatation, narrows to a 

 rounded point. There is no trace of a median keel. It thus resembles the jugal of flabellatus more 

 than that of any other species, the main distinction being the somewhat greater width in the latter. 

 The axis of the jugal is nearly vertical, but inclines slightly backward. The jugal notch is deep, 

 and the infratemporal fossa large and almost quadrangular, instead of being more nearly triangular 

 as in most species. The angles of the fossa are rounded, with the exception of the anteroinferior 

 one. The preorbital fossa lies between the nasal and maxillary, having a slight contact with the jugal 

 toward the rear. The rostral is rather small, lighter and less rugose than in any other form in which 

 this element is preserved, and the inferior border is more nearly horizontal, as the point does not 

 project downward, as is usual. It is deeply excavated beneath, with a fairly sharp but irregular 

 cutting edge, not so sharp nor so perfectly formed as in prorsus, however; this may be an age 

 variation, the serratus skull being the younger. The nasal horn was a separate ossification, and 

 was lost in maceration, but it could have been neither robust nor long. It was transversely com- 

 pressed at the base, and the dorsal outline was probably continuous with that of the nasals as in the 

 prorsus-brevicomus-horridus group, in contrast to that of elatus and calicorms. 



The brow horns were slender and much more erect than in any species other than -flabellatus. 

 As less than one-half their length is preserved in each instance, one cannot be sure of the reversal 

 of the curve either in serratus or flabellatus, although both have been restored as though it were 

 present. There is, however, a boss-like prominence at the base of the horn, in the rear. It is one 

 of a series of three which extend in an oblique line down to the proximal third of the squamosal. 

 This prominence is characteristic of the brow horns of elatus, calicomis, and obtusus, although in 

 these species the continuation of the prominences on to the squamosal is lacking. The base of the 



70 Marsh, O. C, 1890, pp. 81-82. 



71 Hatcher, Marsh, Lull, 1907, Pis. XXVI1-XXIX. 



