42 
possibilities of the structure. In Styracosaurus the six great radiating 
spikes served this purpose, although the arrangement seems poor mechanic- 
ally. . The crest proper is shorter and heavier, and the fenestrse smaller, 
than in Chasmosaurus. Similar strengthening occurs in Centrosaurus. In 
this genus there are hook-like processes extending from the posterior margin 
of the crest forward over the fenestree. Although these processes show 
considerable individual or specific variation, they seem to have formed a 
protection for the fenestrse, which were the weakest parts of the crest, closed 
as they were only by the temporalis muscle. The defensive function be- 
comes completely dominant in the crest of Triceratops , but at the cost of 
reduction of the temporalis muscle. 
Figure 5. Anchiceratops 
longirostris Sternberg, holo- 
type, Geol. Surv., Canada. 
No. 8535, dorsal view of 
crest with temporalis 
muscle (tin.) restored; 
Figure G, Triceratops sp., Geol. Surv., Canada, 
No. 8741, dorsal view of crest, party restored, 
showing restoration of temporalis muscle 
( ini .) ; X 
With such development of the temporalis muscle the ceratopsian 
mandible must have been capable of closing with great force. Tait and 
Brown (10) have suggested that the beaked jaws were used to shear off 
small tree trunks. No doubt the necessary strength was there, if the head 
could have been brought into the required position. In a more normal 
posture the hooked beak, backed by the powerful jaw muscles, would have 
been a very efficient organ for tearing off branches or grubbing up roots. 
THE NECK 
The muscles of this region may be divided into two groups, those hav- 
ing attachment to the fore limb, and those that are anterior continuations 
of the trunk muscles. Only one of the former group will be discussed here. 
Lull (2) has described the muscle attachments visible on the posteroventral 
surface of the skull in Triceratops. The writer accepts the various attach- 
ment areas recognized by Lull, but differs considerably in the identification 
of the particular muscle concerned. 
Capiti-dorsi-clavicularis (trapezius group of mammals) (Figure 9, 
cdc.). The long median groove on the ventral surface of the parietal in 
