VE ls 
The muscles of mastication and the movements of the skull in Lacertilia. 485 
that the lizard’s prey is living; and therefore, it is safe to presume, 
desirous of escape. Supposing the victim to be a worm, the following 
is apparently the manner in which the lizard succeeds in swallowing 
it. From its conformation, the worm must be seized by one end. 
This having been done, in order that deglutition may be accomplished, 
the lizard must again open its mouth to the end that a further hold 
may be obtained upon the elongated prey. The mouth being open, 
were there no provision to prevent it, the squirming worm might 
regain its freedom. This accident, however, is prevented by the ad- 
duction of the previously abducted jaws, which firmly grip that portion 
of the worm which is contained in the mouth. This process is re- 
peated until the whole of the worm has passed into the œsophagus. 
The grip by the pterygoid bones is rendered more secure by the 
pterygoid teeth when such structures are present. 
The abduction of the halves of the mandible is possibly ac- 
companied by a slight rotation of each half about its long axis; a 
similar sort of rotation no doubt taking place in the pterygo-palatine 
arch during abduction, since the upper edge of this moveable section 
of the skull is attached to the bones lying above it. It is conceivable 
that the posterior part of the M. mylo-hyoideus brings about the 
rotation of the mandible. 
This rotatory movement, combined with the abduction described 
above, is doubtless of great value when the food to be dealt with 
possesses a hard outer covering, as, for instance, in the case of a 
beetle. 
There can be no question that the movements of the pterygo- 
palatine arch, and their consequences, are produced by the group of 
three muscles which are buried under the M. capiti-mandibularis and 
M. pterygoideus. From the direction of their fibres, it is evident that 
the Mm. pterygo-sphenoidales posteriores when contracting will pull 
the pterygoid bones forwards and upwards, and in this manner elevate 
the frontal segment of the skull. At the same time adduction of the 
pterygo-palatine arch will be produced. These muscles, as has been 
recently insisted upon by KATHARINER (18), produce much the same 
kind of action in the snakes. 
The Mm. pterygo-parietales doubtless antagonise the foregoing, 
Since, during their contraction, they will draw the parietal and ptery- 
goid bones nearer together, so producing depression of the frontal 
segment. When the mouth is closed it is possible that these muscles 
press the pterygoids against the basipterygoid processes of the sphenoids, 
