EOCERATOPS CANADENSIS, 
13 
three anterior dorsal vertebrae are coossified, and the first 
exhibits a deep cup for articulation with the preceding vertebra. 
The epistemum is a T-shaped bone, thin and keeled on the median 
line below. Length of transverse portion 21 inches.” 
As already pointed out by Hatcher a number of errors were 
included in the above definition. The teeth described are 
those of a trachodont, the supposed epistemum proved to be the 
parietal portion of a frill as recognized by Cope in later descrip- 
tions, and the three vertebrae described as being anterior dorsals 
were found to be cervicals. 
The type material described and figured by Hatcher in his 
monograph includes besides the coossified parietals, a sacrum, 
and cervical, dorsal, and caudal vertebrae. Limb bones, a 
scapula and coracoid, an ilium, and an ischium are also figured 
and described as pertaining to M. crassus, and a left postfrontal 
bone bearing a horn-core, mentioned by Cope, is referred with 
a query to the same species. Hatcher was of the opinion (Mono- 
graph, page 76) that the parietals, the postfrontal, and the sacrum 
pertained to three different individuals. 
That the parietals and the remainder of the above-mentioned 
material, belong to the same species or even the same genus is 
doubtful. 
In comparing the parietals of Monoclonius with those of the 
wonderfully preserved skulls of the homed dinosaurs from 
Alberta a general resemblance to both Centrosaurus and Styra- 
cosaurus is apparent. 
The parietal portion of the frill of M. crassus appears to 
be a much worn or weathered specimen, judging from the original 
figure in the American Naturalist, Vol. XXIII, 1889, and from 
the seemingly more exact one in Hatcher’s monograph. In general 
proportions it bears some resemblance to the same part of 
the frill in Centrosaurus if the fontanelles are as large as 
they are suggested to be in the above figures. If, on the 
other hand, the fontanelles of crassus were of less ample 
proportions than indicated in these figures, parietals of Styra- 
cosaurus, which had been subjected to severe weathering after 
the large posterior bony outgrowths had been broken off close 
to their base, would have much the appearance of the frill speci- 
men of M. crassus. 
