350 DAVIDSON BLACK 
developed descending rami of the suprasylvian. There is no 
indication of an arcuate constellation. 
(5) Procamelus occidentalis (figure 14). This figure has been 
inserted in the present series for purposes of comparison with 
the modern camel. The endocranial cast of this form has been 
described by Cope, from whose drawing (7) the outline in ques- 
tion has been taken. 
The processus acuminis of the pseudosylvian fossa is seen to’ 
be well developed and only separated from the suprasylvian 
sulcus by a small space. The groove labelled descending ramus 
of the suprasylvian in figure 14, has precisely similar relations to 
the pseudosylvian fossa and upturned ramus posterior ectosylvil 
as the sulcus bearing the same name in the pig. 
The long horizontal ramus of the suprasylvian, together with 
the lateral and entolateral sulci, is simple and linear, but without 
a re-examination of the cast their frontal relations are not clear. 
(6) Camelus dromedarius (figure 15). The above figure has 
been taken from Flatau and Jacobson’s text (12, p. 482). Their 
- drawing has been enlarged in the present instance until the 
fronto-occipital diameter was equal to this dimension in an adult 
skull of Camelus in the Reserve Anatomical Museum collection. 
In this way some idea of relative size can be gained. 
In the camel the suprasylvian sulcus is quite dorsally placed, 
while the processus acuminis of the pseudosylvian is short. There 
is thus a broad area between these two sulci, which is marked 
by certain compensating furrows similar in nature to the arcuate 
constellation of Giraffidae. It is evident, however, from the 
arrangement of the sulci in the ancestral Procamelus (26, p. 300) 
that the arcuate group of sulci has been recently acquired in the 
camel. 
The sulcus which I have labelled R. desc. ss. is termed by 
Flatau and Jacobson the ‘fissura postica’ or ‘fissura suprasylvia 
posterior. ’ : 
(7) Hquus caballus (figure 16). Among Perissodactyla in 
general, the presence of an arcuate constellation similar to that 
described in the Giraffidae, is a characteristic feature. In the 
