476 O0. CHARNOCK BRADLEY, 
Nirzscu (7) published a paper dealing with this question; and TEUT- 
LEBEN (8) in 1874 directed some attention to the subject. But after 
an examination of the fresh skull of an ordinary lizard one is forced 
to the conclusion that matters are not quite so simple as Nirzscu 
and TEUTLEBEN made out. 
Because of this deficiency in the knowledge of the subject, Pro- 
fessor GAUPP recently suggested that I should make a series of ob- 
servations on the jaw-muscles of several lizards. For his primary 
suggestion, and for continued and most generous advice, as well as 
for most of the material made use of, I cannot sufficiently express my 
thanks to Prof. GAupp. I have also to thank Geh. Hofrath Prof. 
WIEDERSHEIM for permission to work in his Laboratory. 
On account of its conveniently large size, Varanus bivittatus was 
examined in the first instance; and it was found that this animal 
formed a very excellent type with which to compare the muscles, etc. 
of the other lizards. The differences between Varanus and the smaller 
lizards dissected was found to be one of detail only, and not of 
essentials. In addition to Varanus, the disposition of the muscles in 
Lacerta agilis and viridis, Agama colonorum, Gecko stentor and Pseudo- 
pus pallasii has also been observed. The process of mastication 
was watched in the living Lacerta agilis and viridis; and in these 
animals the fresh skull was examined in order to discover the possi- 
bilities of movement between its various parts. 
The muscles of Varanus will be described in detail and any 
differences found in the other animals will be noted. 
Concerning Mm. mylo-hyoideus and parieto-mandibularis (Fig. 1 
M. par-mand) little need be said as they form part of a very ela- 
borate investigation by RuGEe (9). Moreover, their actions as muscles 
of mastication are not difficult of appreciation. 
M. capiti mandibularis (Fig. 1 M.cap-mand). 
In all lizards this is a large and powerful muscle. In Varanus 
it takes origin from the post-frontal, quadrato-jugal, squamous, prootic 
and quadrate bones. It has a tendinous insertion into the Os com- 
plementare, and a fleshy attachment along the upper border of the 
mandible (supra-angular and articular) from the Os complementare 
to the articulation for the mandible. Its fibres do not all run in the 
same direction as is shown in Fig. 1. A few of the more superficial 
fibres, taking origin from the quadrate bone, run more obliquely than 
the rest. This, however, seems to be a peculiarity of Varanus, since 
