538 



MR. D. W. DEVANESEN ON THE 



of the ilia as well as that of the urostyle denotes a primitive 

 feature, or whether it is a sign of degeneration, cannot be easily 

 settled for the reason indicated above. At the free anterior end 

 of each ilium there is found, attached to its outer side, a peculiar 

 cartilaginous appendage. This has the shape of a plate, which, 

 by folding on itself, encloses a groove into which is received the 

 cartilaginous free edge of a sacral diapophysis. Thus the sacrum 

 movably articulates with the ilium (text-figs. 8 &■ 10). In other 

 words, the pelvic girdle, by means of the ilia, forms a gliding 

 joint with the backbone through the sacrum. On the contrary, 

 the sacral transverse processes in Rana are immovably attached 

 by tissue to the anterior ends of the ilia, and consequently no 

 movement in the manner mentioned above could take place. I 

 was able to observe in emaciated specimens the ilia moving 



Text-figure 8 (A and B). 

 A. B. 



C.A 



C.A. 



I., ilii 



C.A., 



A. The pelvic girdle of Cacopus systonia viewed from above, 

 cartilaginous appendage of the latter. 



B. The same girdle seen sidewaj's. P., pubis ; I.S., ischium ; A., acetabulum. 



obliquely backward and forward during the act of burrowing. 

 I should therefore suppose that this gliding joint has something 

 to do with the same habit of burrowing. 



Beddard (1, p. 12), with reference to a cartilaginous plate 

 unconnected with the ilium but covering the sacral diapophyses 

 in Breviceps verrucosus, remarks as follows : — " I imagine that 

 this cartilage belongs to the ilium, and that it is in consequence 

 related to it as the suprascapula is to the scapula. We have, in 

 fact, in this frog an exaggeration of the grooving which the 

 anterior end of other forms shows at its line of articulation with 

 the sacral vertebra. It is, moreover, interesting to observe that 

 we find in this fiog a kind of foreshadowing of the relations 

 which the ilia bear to the sacrum in the higher Sauropsida, 



