ANATOMY OF CACOPUS SYSTOMA, 533 



begins posteriorly aboiit the middle of the thighs*. This, I 

 should think, improves upon the efiect produced by the viscera. 

 The enlarged lymph-sinuses, with the lymph and fat-bodies con- 

 tained therein, enhance the stout shape. 



The purpose of the enlarged lymph-spaces of the two toads of 

 this genus is perhaps to be sought in their fossorial habits. The 

 liberally secreted lymph may serve to protect the internal organs 

 from injuries incidental to animals with such habits. The muscles 

 of the abdomen in 0. systoma, chiefly the rectus abdominis, form 

 a weak protection, as they are stretched to their utmost capacity 

 by the pressure of the enormously-developed viscera. The 

 presence of a fluid between the latter and the skin must, under 

 such circumstances, serve to diminish the chances of injury from 

 outside. This supposition is strengthened by the fact that larger 

 quantities of lymph were found in specimens obtained during 

 the dry Aveather than in those examined during the wet-season. 



5. The Axial Skeleton. 



An examination of the bones of the head revealed certain facts 

 which, in my opinion, account for the narrow mouth of this toad 

 in particular, and probably also for that of several other members 

 of the same family in general. While the contour of the mouth 

 which corresponds to the distal circumference of the skull, is a 

 parabola in liana, the same has been in this animal reduced to 

 a mere arc. Assuming that the skull -morphology in Bana is 

 primitive, one can trace the narrow mouth in question to a 

 generally vestigial condition of most of the bones of the suspen- 

 soi'ium. Thus the squamosal has lost the anterior arm or the 

 zygomatic process, what remains probably corresponding to the 

 middle t and posterior arms of the same in Rana (text-fig. 4 A). 

 The palatine, for another instance, is so inconspicuous, being 

 about 3 mm. long, that it can only be found in skulls very care- 

 fully prepared. The remaining bones of the suspensorium also 

 exhibit in a greater or a lesser degree the same degenerate state ; 

 the cumulative efl:ect of this, in all probability, was the forward 

 displacement of the articular head for the lower jaw. For, a line 

 drawn along the suture between the nasals and the fronto- 

 parietals cuts the orbital fossae at about the middle and passes 

 through the heads in question (text-fig. 4 C), whereas in Rana the 

 same line lies far in front of the last (text-fig. 4 D). This shifting 

 of the articular heads necessitated by the vestigial condition of 

 the bones of the jaws has probably led to a diminution in the 

 contour of the mouth. 



The cranium as a whole is remarkable for its shortness and 



* This character is greatly exaggerated in C. glohulosus, judging b}' the specimen 

 in the Government Museum, Madras. Beddard (1) has recorded a similar condition , 

 still more pronounced in Brevioeps verrucosus, an Ethiopian Eng3^stomatid. 



t The presence of this middle arm is also doubtful, as the attachment with the 

 'pro-otic is by means of a ligament which may, however, be taken to represent this 

 arm. 



37* 



