92 



THE CERATOPSIA. 



closely allied to if not identical with the M. crassus of Cope. The nasal horn and orbit are 

 very large when compared with the occipital condyle, the maxillaries, and quadrate. 



The peculiar parietal (see footnote b, p. 93) associated by Lambe with the type of M. dawsoni 

 I regard as pertaining to a distinct species and perhaps also to a distinct genus. The median 

 parietal bar is very heavy and deeply emarginate posteriorly, where on either side it gives 

 off an elongated process which is pointed and curves inward and slightly downward. The 

 bases of these processes are separated from one another by a distance of 300 mm. They are 

 each 109 mm. in length, have a breadth of 112 mm. at the base, and a thickness of 30 mm. 

 They are acutely pointed, have rugose surfaces with deep vascular grooves, and in life were 

 evidently insheathed in horn. The posterior border of the parietal between the bases of these 

 processes is very thick and round. On the superior surface, in the middle just in front of the 

 posterior border, there is a rather deep concavity. The median bar of the parietal is very 

 thick throughout its entire length. Its superior surface is marked by a number of very gentle 

 elevations; it is rugose and shows shallow vascular impressions. Beside the processes already 

 mentioned as present on the posterior portion of the parietals, there is on either side a series 

 of seven emargina-tions on the parietal borders separated by as many prominences. The 



Fig. 95. — The same sacrum as in fig. 94; right lateral aspect, about one-seventh natural size, a, a. Facet for ilium; d, diapophysis; np, neu- 

 ral platform; ns, neural spine. After Lambe. 



posterior of these prominences are the larger, and each bears evidence of having supported a 

 distinct epoccipital bone during the life of the animal, save perhaps the two anterior, which 

 appear to have been overlapped by the squamosal, since the parietal in this region presents a 

 rather distinct sutural surface for contact with the squamosal. The parietals on either side 

 of the median bar present a large fontanelle, and the margin of bone inclosing this is very thin. 

 These fontanelles have a length of 292 mm. and a breadth of 254 mm. The parietal bar is 

 concave on its inferior surface, especially anteriorly. At its anterior extremity it presents a 

 number of cavities and articulates with the postfrontals. a 



The sacrum described and figured by Lambe and provisionally associated with the present 

 species does not belong to the Ceratopsia. It is clearly the sacrum of one of the Ornithopoda 

 and belongs without doubt to some species of Trachodon. 



The nasal horn (No. 190, Geol. Surv. Canada) figured by Lambe and reproduced here in 

 PI. XVIII, figs. 1 and 2, though referred by him with a query to M. dawsoni, resembles more 

 nearly the same element in M. recurvicornis Cope. It differs from that element in M. dawsoni 

 by curving forward as in M. recurvicornis instead of backward as in the type of M. dawsoni. 



a See fig. 93 and PI. XXIV. 



