12 
MUSEUM BULLETIN NO. 12. 
Also in Chasmosaurus belli (Plate VIII), of which the entire 
skull (including the lower jaw) is known, the brow-horns differ 
entirely from those of Ceratops. 
The genus Monoclonius, Cope, with M. crassus as the type 
species, is unfortunately also in a very unsatisfactory state. 
According to Hatcher (Monograph on the Ceratopsia, 1907, 
page 73) the actual type material described by Cope from the 
Judith River district, Montana, U.S.A., was apparently “of a 
composite nature and pertained to two or more individuals.” 
The genus and species were originally defined by Cope as 
follows: — 
“Char. gen. — Teeth with obliquely truncate face and dis- 
tinct root, which is grooved for the successional tooth on the front. 
No external cementum layer, caudal vertebrae biconcave, and 
brim narrow. Fore limbs large and massive.” 
“The teeth of this genus resemble those of Hadrosaurus , 
and like them are replaced from the “front,” an arrangement 
which precludes the possibility of more than one series of teeth 
being in functional use at one time. The robust fore limbs 
and elongate ilium distinguish 1 Monoclonius from Hadrosaurus. 
From Trachodon it differs in the absence of the rough cementum 
layer on the back of the tooth.” 
“Char, specif . — The faces of the teeth are acuminate, oval 
in form and are divided by an elevated keel, which is median 
above, but turns to one side at the base. Margin, crenate, the 
grooves extending more or less on the crown ‘back/ which is 
otherwise smooth.” 
“Sacrum with ten vertebrae, the last centrum much com- 
pressed, the diapophyses extending horizontally from the neural 
arch above, and connected by a vertical lamina with the iliac 
supports; length 27*33 inches. The bones of the limbs are ro- 
bust, the hinder the longer, but not so much so as in some other 
genera. Length of femur 22 inches; width proximally, 7*4 
inches; distally 6 inches. Length of tibia 20 inches; greatest 
diameter, proximally, 8 inches; distally, 7*25 inches. The 
1 In the original description the word Monoclonius was by mistake printed 
Diclonius. 
