15t) MR. F. K. BEDDAIJU ox A PAKASTERNUM [Juiie 7, 



ill Tiliqua was an iiii})eii'ect i-epreseiitatioii of that occui'i-ing in the 

 Ohampeleon iiiid other lizai-ds, whei-e a. numbei" of true ribs join 

 venti-ally behind the sternnni. Thus in Acontias and Ty2Mo- 

 saurus, of which the foi-inei- is a near ally of Tiliqua, there 

 are present these post-sternal libs meeting in the middle line, 

 M.nd thus simulating abdominal riljs *. In the Ohanifeleon the 

 most venti-al layei- of the abdominal musculature is so thin that it 

 i-equii-es a careful dissection to show that the ventrally meeting 

 ribs do not lie in this layer but in the deepei' layer. In Tiliqua, 

 on the other liand, the ventivnl musculature is thick, and the two 



Text-fip-. 29. 



Alxloiiiiual ribs of Tiliqua scincoides. 

 A points to one of these ribs. A meshwork of tendons lies between and over them. 



layers are easily distinguishable. When the venti'almost layer is 

 raised, the abdominal ribs are carried with it, and are seen to end 

 off in it Avitli slightly forwardly- curved latei'al ends. But — more 

 important than this — on the deeper layer of the musculature are 

 two or three cartilaginous bars, lying obliquely (see text-fig. 30, 

 p. 157), which are clearly the ventral portions of true ribs such as in 

 Acontias make complete hoops. The discovery of these entirely 

 sets at rest any doubt as to the fact that the bai's of cartilage which 

 lie superficially are I'eally quite comparable to a parasternum. The 

 ti-ue venti-al moieties of the i-ibs are not in connection with theii' 

 vertebral portions, so far as I have been able to ascertain. They 

 would thus be very I'eadily lost in macerated skeletons, and might 

 even be overlooked in a dissection. In his ' Catalogue of Lizards 

 * Peters, ' Reise nach Mossambique,' Amphibia, pis. xii. & xiii. 



