890 MR. F. E. BEDDARD ON THE [Nov. 26; 



PelobatidiB are present, a.ncl have the origin, course, and insertion 

 as in Megalophrys, &c, Tliey ai-e completely superficial and visible 

 on the internal aspect of the thigh only. There is no deeper 

 muscle which could correspond to the semitendinosus of Rana. 

 I find on a dissection of another example of Pipa that the 

 insertion of the muscles (at any rate in that individual) is a little 

 different from my description of the same in the paper already 

 referred to. The two muscles are free from each other at their 

 origin and also for the greater part of their coui-se — and in this 

 they differ from the corresponding muscles of the Pelobatidas — 

 but unite to form a common tendon which interposes itself 

 between the two recti interni muscles (or gracilis), and is therefore 

 inserted ventral of one and dorsal of the other. In spite of these 

 differences, it is I think reasonable to assume that there is an 

 homology between these muscles in Pipa and those which have 

 just been described in the above-mentioned genera of the Pelo- 

 batidse. This resemblance is in itself an interesting fact, and is 

 to be added to those which I have already referred to and shall 

 have occasion to refer to later. 



My own observations upon the anatomy of Pipa and Xenopus 

 and those subsequently published by Dr. Ridewood, which I have 

 occasion to refer to several times in the course of the present 

 communication, have certainly strengthened the opinion that 

 there is a relationship between Pipa and Xenopus closer than 

 that which ties either of these genera to any other genus *, and 

 that the group Aglossa is fully justified. It is not unreasonable,, 

 therefore, to compare the thigh-muscles in the two. I have again 

 dissected Xenopihs in case any eiTor might have crept into my 

 former account of that Frog, and find that the facts relating to 

 the miTSCulature of the thigh are as I there stated them f. I 

 believe, moreover, that my interpretation of the thigh-muscles of 

 Xenopus was more correct than of those of Pijya. The sartorius 

 of Xe7iopus is largely fused with the semitendinosus, but has a 

 separate insertion. The loss of this and the reduction in size of 

 the sartorius (from before backwards) would bring about a state 

 of afiairs such as exists in Pipa and the Pelobatidfe, where the 

 presumed sartorius is not only thinner but has a more posterior 

 origin ; the loss of the anterior portion of the muscle in Xenopus 

 would obviously bring about such a result. These suggestions 

 are of course based upon the supposition that there is likely to be 

 a resemblance in the musculature of Xenopus and of Pipa. And 

 in any case the views which I have ventured to express seem to 

 me to be the most probable ones. On general grounds one might 

 perhaps be tempted to look for a closer likeness between the 

 Pelobatidfe and the Ranidpe than between the Pelobatida3 and the 

 Aglossa ; but the facts which have just been considered afi"ord no 

 basis for a comparison on these lines. Finally, as concerns the 

 thigh-muscles, I may point out that the exposure of the insertion 



* Except of course Hymenocliinis, the third genus of Aglossa. 

 t P. Z. S. 1895, p. 844. 



