1905. ] OF THE YELLOW-THROATED LIZARD. 257 
position of Gerrhosaurus, that this lizard agrees absolutely and in 
every detail, so far as the jugal ligament is concerned, with the 
skink Humeces. 
The final stage in the arrangement of the jugal ligament is 
shown in Physignathus. In this lizard the ligament is attached. 
firmly to the bones at either extremity, and has entirely lost 
its presumably original connection with the skin. Moreover, in 
the last-named lizard, the ligament is divisible into two regions. 
There is, first of all, a stronger narrow ligament which occupies 
exactly the position of the bony quadrato-jugal bar in Hatteria, 
and above this and in part overlapped by it is a thinner but still 
stout sheet of ligament which entirely fills up the temporal vacuity. 
This state of affairs does not exist at all in Gerrhosaurus and 
Humeces. It is distinctly suggestive of the complete obliteration 
of the lower temporal vacuity in certain Vertebrates. 
In view of the fact that bones in some cases can be shown to 
degenerate into ligaments, it is not certain that the stages sketched 
out above may not be read in the inverse order. For example, 
the lower part of the fibula is ligamentous in Birds; but it is not 
to be assumed that here there is anything but a degeneration of 
the bone into ligament. The facts which have been detailed above 
coneerning certain Lizards do not, however, appear to me to point 
to a reduction from a state of affairs such as is found in Hatteria. 
If we were only acquainted with the condition observable in 
Physignathus and Iguana, such a view might indeed be held. 
The bone, it would be urged, has degenerated into ligament in the 
one case, and has finally disappeared in the other. But the 
conditions to be seen in Gerrhosaurus and in Hwmeces would seem 
to negative such a supposition. 
Peritoneal Folds and Celom. 
Although the suspension of the alimentary tract and the other 
viscera contained in the ccelom is broadly like that of many other 
Lacertilia, there are some differences of detail which require 
attention. 
In the female example the line of attachment of the oviducal 
membrane, which diverges laterally on each side, marks off 
sharply the posterior pigmented area of the coelomic membrane 
from the anterior non-pigmented or less pigmentedarea. This is 
quite a common and well-known arrangement among the Lacertilia. 
The reason why I bring the matter forward here, is that Gerrho- 
saurus differs from Humeces, where there is no such differentiation 
of pigmented and non-pigmented areas*, and because the pig- 
* This is not, however, a distinctive mark of difference from the Scincide and of 
likeness to Lacerta. Lacerta shows this sharp demarcation; but there are varying 
degrees among the Scincide. In Hwmeces there is hardly any pigmentation ; in 
Tiliqua scincoides there is a moderate amount, but evenly spread through the body- 
cavity (in a male). In Macroscineus cocteaui (female), however, the oviducal 
membrane marks off two areas; but the posterior area is not so deeply pigmented as 
in Gerrhosaurus. 
Proc. Zoou. Soc.—1905, Vou. II. No. XVII. 17 
