ARRHINOCF.RATOPS BRACHYOPS 107 



Doctor Parks goes on to say: "The nasal horn core is apparently absent, but the nasal bone is 

 sharp above and somewhat rugose, suggesting that it may have carried a horny sheath. The nasal 

 bone rises very abruptly, posterior to the suture with the rostral, suggesting the condition that 

 maintains in Triceratops prorsus, but there is no trace of a horn core nor of an epinasal; neither 

 does the surface of the bone indicate that a structure of this kind has been lost." There is, if any- 

 thing, more of an indication of a nasal horn than in the type of Triceratops obtusus at the United 

 States National Museum. And the position of the horn-like area lies over the anterior margin of 

 the narial opening as in the Lance genus, not above the posterior margin as in all Belly River forms. 



The face is characteristically short, resembling Chasmosaunis, and the crest is also typical, being 

 subquadrate in outline and very flat toward the rear. Herein it again resembles both Chasmo- 

 SOUTHS and the Lance Torosaurus, as it also does in the extremely elongate squamosals which, how- 

 ever, are relatively broader anteriorly than in either genus. The parietal fenestrae are smaller than 

 in Chssmosaurus, and are narrower, though relatively longer, than in Torosaurus. The jugals are 

 extremely long fore and aft, especially in their anterior process which overlaps the maxillary to a 

 remarkable extent. This, as Parks says, makes the distance between the maxillary and the orbit 

 strikingly great. The infratemporal arcade is long and straight, which gives the infratemporal fossa 

 a subtriangular shape, with a sharp apex and rounded base. 



The supraorbital horn cores are stout, tapering sharply, circular in cross-section at their base 

 instead of being laterally compressed as in Torosaurus. There are the usual vascular impressions 

 and, in addition, each bears a shallow longitudinal sulcation extending for about 250 mm. from the 

 tip downward, in line with the edge of the orbital rim. The horn cores are rather close together at 

 their base and flare strongly outward and then curve forward in a manner similar to those of the 

 paratype of Anchiceratops ornatus described by Brown. 



The crest, composed of the usual elements, squamosals and parietals, is subquadrangular, with 

 somewhat curved lateral and straight posterior margins. It is deeply marked by vascular impres- 

 sions not only on its dorsal side, but over as great a part of the ventral aspect as in any other cera- 

 topsian skull. The parietal fenestrae are elongated, and oval in shape. Another opening, doubtless 

 of a pathologic nature, pierces the left squamosal. 



The orbits are elliptical, with the long diameter directed upward and backward. They almost 

 entirely underlie the anterior half of the horn core, being both in form and position very similar to 

 the type of Triceratops obtusus, and differing from Diceratops in which the front margin of the 

 horn would, if continued downward, about bisect the orbit. 



Parks stresses the absence of sutures in the occipital condyle, the presence of which would indi- 

 cate that the exoccipitals form part of it. "Nevertheless," he says, "it would be hazardous to con- 

 clude that the condyle is composed of the basioccipital alone." I know of but twoinstances among 

 the horned dinosaurs in which any trace of these sutures is present, indicating the tripartite character 

 of this element. One is that of a detached condyle belonging to the type skull of Torosaurus gladius 

 (No. 1831 Y.P.M.) figured by Hatcher in the Ceratopsia Monograph (Fig. 7), in which the sutures 

 are clearly visible on the articular surface; the other is the plesiotype of Triceratops elatus (No. 

 4805 U.S.N.M.) in which the sutures show at the fractured base but not on the surface. The 

 assumption is, however, that every ceratopsian condyle includes portions of both exoccipitals and the 

 basioccipital. 



Quoting from Parks again, "The anterior tips of the nasals embrace the posterior end of the 

 rostral," which, if true, is a very unusual occurrence, for generally, if not always, the premaxillaries 

 are interposed between the rostral and nasal bones. As usual, the nasals form a part of the bony 

 nasal septum though the greater portion is of premaxillary origin. That portion of the nasals which 

 functioned as a horn core is trihedral in shape. It arises abruptly in front, forming a triangular 

 face, while the two plane, sloping, lateral sides meet above in a sharp somewhat convex ridge 

 extending backward halfway to the orbits. The bone is quite rugose on the anterior face and slightly 

 so on the left side at the anterior end. There must have been a close-fitting horny investment, but 

 hardly a progressively growing horn as in the supraorbitals, for the deep, vascular impressions 

 present in the latter are absent in the nasal region. 



