The muscles of mastication and the movements of the skull in Lacertilia. 477 
a similar arrangement was not found in the other lizards dissected. 
It is difficult, therefore, to say what significance it has; if, indeed, it 
has any. When this muscle is carefully removed a small portion of it, 
situated deeply, appears to have a separate entity (Fig. 2 A). This 
consists of a thin triangular strip arising by its base from the prootic 
bone and inserted into the upper border of the supra-angular about 
the middle of its length. One does not feel inclined to lay any 
particular stress upon this portion of the muscle since it could not 
be distinguished in the other specimens examined. In Varanus, cer- 
tainly, it is easily dissected; the dissection being all the more readily 
made from the circumstance that the large nerve to the M. capiti- 
mandibularis curves over its lateral face, so making a very obvious 
distinction between it and the overlying muscular mass. 
There is not sufficient difference in the disposition of this muscle 
in the other animals dissected to make additional discriptions neces- 
sary. What slight differences there are are due to modifications of skull 
form. It is perhaps worthy of note that in all the origin was from 
the parietal, prootic and quadrate bones at least (in some the origin 
was more extensive, e. g. Varanus). 
M. pterygoideus (Figs. 2 and 3 M.ptery' and M. ptery“). 
The descriptions of previous writers had prepared one to expect 
that this muscle would be very variable. For instance, MıvArT de- 
scribes its origin in Iguana tuberculata and Chamaeleon parsonii as 
being from the pterygoid bone; SANDERS in Platydactylus japonicus 
from the prootic and columella, and in Liolepis belli from the parietal 
and prootic bones. In the specimens dissected it was certainly found 
to be variable, but the variability was in the direction of volume 
rather than origin. In Varanus the muscle is large, and can be said 
to consist of two portions, the superficial of which arises from the 
parietal bone and is inserted into the Os complementare along with 
the M. capiti-mandibularis (Figs. 2 and 3 M.ptery). The deeper 
portion of this muscle has its fibres running in a somewhat more 
vertical direction. It takes origin from the whole of the columella 
with the exception of its lowest part, and is inserted into the mandible 
behind and within the superficial portion (Figs. 2 and 3 M. ptery"). 
In Lacerta and Pseudopus the attachments are the same, but it is 
not possible to distinguish two portions. In Pseudopus the muscle is 
as powerful as in Varanus; in Lacerta it is not so large. In Gecko 
and Agama it is much smaller, and evidently corresponds to the 
ol 
