256 MR. F. E. BEDDARD ON tHE ANATOMY [June 6, 
5. Some Notes upon the Anatomy of the Yellow-throated 
Lizard, Gerrhosaurus flavigularis. By F. EH. Bepparp, 
F.R.S., Prosector to the Society. 
[Received May 17, 1905.] 
(Text-figures 33-38.) 
Apart from osteology * and a few scattered notes, which will 
be veferred to in the course of the present communication, there 
does not appear to be a great deal known about the internal 
structure of Gerrhosaurus. Inasmuch as this Lizard is regarded, 
from the point of view of external characters and osteology, as 
being exactly intermediate between the Lacertidz and Scincide ‘7, 
it seemed to me interesting to attempt a criticism or confirmation 
of this view, while recording any new facts which an investigation 
of Gerrhosaurus flavigularis might bring to light. 
Jugal Ligament. 
Many, but not all, of the Lacertilia possess, as is well known, 
a jugal ligament, which Huxley compared to the bony lower 
temporal arcade of Hatteria. The exact relationships of this 
ligament have not, I believe, been described in some of the 
Lizards in which I shall now proceed to detail the arrangement. 
Tt is possible to recognise several stages in the conditions of the 
jugal ligament, which may represent evolutionary stages, though 
it is, of course, not implied that the genera to be mentioned are 
genetically connected in the order named. 
In Jguana tuberculata the ligament as a distinct structure 1s 
totally absent. On cutting through the skin covering the “ cheek,” 
the muscles and bones of this region of the skull are at once 
arrived at. It appeared to me, however, that the subcutaneous 
connective tissue, which is dense and white in most parts of the 
body, was rather denser and whiter in the region where the jugal 
ligament would be were it present. It is possible, in fact, that in 
this lizard an early stage is met with—that the ligament is not 
yet differentiated from the general connective tissue of the skin. 
On the other hand, it cannot be denied that the same fact may be 
explained on the theory that the ligament has disappeared. In 
any case, Gerrhosaurus offers an intermediate condition. In this 
reptile the ligament in question is anchored firmly to the quadrate 
behind, but in front it is not attached to the jugal bone but to 
one of the bony scales which cover the face in this region. That 
is to say, the ligament has not as yet completely detached itself 
from the skin. So, at any rate, the facts seem to indicate. It is 
important to notice in connection with the main object of the 
present communication, viz., to attempt to fix the systematic 
* Siebenrock, Ann. k. nat. Hofmus. Wien, vii. 1892. 
+ Boulenger, Cat. of Lizards. 
