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 Eumeces. 



The final stage in the arrangement of the jugal ligament is 

 sho\\ai 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 

 Eumeces. It is distinctly suggestive of the complete obliteration 

 of the lower temporal vacviity 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 

 concerning 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 Igiumia, 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 Eumeces would seem 

 to negative such a supposition. 



Peritoneal Folds and Ccelom. 



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 coslomic membrane 

 from the anterior non-pigmented or less pigmented area. 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 Eumeces, where there is no such differentiation 

 of pigmented and non-pigmented areas *, and because the pig- 



* This is not, liowever, a distinctive mark of difference from the Scincidse and of 

 likeness to Lacerta. Lacerta shows this sharp demarcation; but there are var3'ing- 

 degrees among the Scincidoe. In Eumeces there is hardly any pigmentation ; in 

 Tiliqua scincoides there is a moderate amount, but evenly spread through the body- 

 cavity (in a male). In Ilacroscincus cocteaui (female), however, the oviducal 

 membrane marks off two areas ; but the posterior area is not so deeply pigmented as 

 in Gerrliosaurtis. 



Proc. Zool. Soc— 1905, Yol. II. No. XYII. 17 



