MONOCLONIUS RECURVICORNIS. 85 



The peduncle of the condyle is somewhat constricted hi front of the articular surface, and it is ; 

 subcircular in cross section. The foramen magnum is small, compared with the size of the 

 condyle, and circular in outline; it is inclosed by the exoccipitals and supraoccipitals. I am 

 unable to determine the character or position of the other foramina mentioned by Cope in his 

 description of this specimen. a 



The supraorbital horn cores are short, stout, and abruptly pointed at the apex. Near 

 the base they are subtriangular, becoming somewhat compressed near the apex. Cope asserted 

 that the base of the horn core is solid, but I find that it is cavernous, the cavities being filled 

 with matrix which in color and texture resembles the surrounding bone. The right horn 

 core is somewhat more slender and a little longer than the left. In proportion to the nasal horn, 

 the frontal horns are small when compared with those of later genera of Ceratopsia from the 

 Laramie of Wyoming, Montana, and Colorado. Just in front of the right supraorbital horn core : 

 there is on the frontal a prominence with the apex missing, presenting the characters of a 

 diminutive horn core. Unfortunately the frontal of the opposite side is wanting, so that it 

 is impossible to determine whether a similar prominence was present on the opposite side. 

 This prominence is subtriangular in cross section, it is directed anteriorly, and its form and 

 surface markings would indicate that it also bore a horn. 



The L-shaped bone described by Cope is in reality the nasal horn core and a portion of the 

 nasals with which the horn core is coossified, as was suggested by Cope in his original description 

 and definitely stated and figured by him in his later diagnosis of the species. The nasal horn 

 core is massive and curves strongly forward, thus suggesting the very appropriate specific 

 name. It is split throughout its entire length. The line and place of fracture seem to have 

 been determined by a suture. This is especially suggested by the character of the surface 

 near the base of the fractured area, and it would seem to indicate that the nasal horn core in 

 the present specimen was made up in part by the nasals- and in part by a bone derived from a 

 separate center of ossification instead of by the nasals alone, as has very generally been believed- 

 Assuming that this nasal horn core did spring jointly from the nasals and a distinct ossification,, 

 only that portion represented by the latter element has been preserved in the present specimen- 

 The portion preserved shows that the nasal horn core was somewhat more massive than the 

 frontal horn cores and that it was much compressed distally and with the antero-posterior 

 diameter exceeding the transverse throughout its entire length. The external surface, like 

 that of the supraorbital horn cores, is marked by deep grooves, indicating that hi life these 

 elements were insheathed by some substance, which most likely partook of the nature of 

 horns, often assuming large and formidable proportions. From the base of this horn core- 

 the nasals narrow rapidly in front, and thus appear acutely .wedge-shaped when viewed from 

 above. The narial septum is strong, and there is on either side on the inferior surface of the 

 nasals just beneath and in front of the base of the nasal horn core a smooth, shallow, concave 

 area. Posterior to these concavities the roof of the nasal aperture presents a broad, flat surface 

 without a narial septum, the narial apertures of either side being confluent from this point 

 backward. 



Associated with the type is a considerable fragment of bone which I have identified as the 

 proximal portion of the left jugal, showing a considerable portion of the orbital border and of 

 the opposite free border of this bone, as seen just below its union with the squamosal. The 

 external surface of this bone is very rugose, and just below the inferior border of the orbit, 

 there is quite a prominent tuberosity. 



A fragment of the margin of the posterior border of the right squamosal is preserved. It 

 shows three distinct emarginations separated by four prominences, and two of the latter bear 

 epoccipitals. One of these is very small, and both show* distinct sutural connections with the 

 bone itself. The portion preserved suggests that the squamosal was very stout and of consid- 

 erable size. Neither the superior nor inferior surfaces present the vascular grooves to be seen 

 on the squamosals of most other members of the Ceratopsia, but are quite smooth, indicating 

 that the bone was embedded in flesh or, what appears to me more probable, that it pertained 



n Bull. U. S. Geol. and Geog. Surv. Terr., vol. 3, pp. 588-594. 



