1895.] MtJSCTJLAB AJfATOMT OF XENOPIJS. 845 



any marked degree, nearly meet those of the upwardly running 

 " musculris pulmonum proprius.^' 



It is evident, therefore, that the " diaphragm " of Xenopus is in 

 complexity markedly in advance of that of Rana and closely 

 resembles that of Pipa. 



§ Myology. 



I have not attempted even so complete an account of the myology 

 of Xenopus as I have of Pipa, incomplete though that was. I have 

 contented myself with a description of some of the more important 

 muscles which show variations in different types, and from which 

 therefore it may be possible to draw conclusions as to affinities 

 with the very few types of Anurous Amphibians whose myology 

 is known. I have principally made use of Dr. Haslam's translation 

 of Ecker's ' Anatomy of the Frog " ^ as the basis of my comparisons; 

 but I have dissected aU the muscles referred to in a specimen of 

 the large Solomon Island Frog, Rana guppyi. 



The Rectus abdominis is a broad muscle which arises not only 

 from the extremity of the pubis but also from the fascia of the 

 thigh, as shown in the accompanWng illustration (woodcut fig. 3) ; 

 possibly, however, the muscle only arises from the cartilaginous 

 plate at the end of the pubis (the prepubis), as I cannot distin- 

 guish any distinct line of demarcation between it and the adjacent 

 obliquus internus. The fibres pass forward and diverge beneath 

 the end of the sternum into the two recti, which are inserted under- 

 neath the sternum. 



Obliquus internus. As has been just mentioned, this muscle 

 appears to be quite continuous with the last ; but as a portion of 

 the entire muscle underlies the obliquus eo:ternus and gives off a 

 branch to the lung, it must, I think, be regarded as obliquus internus. 

 It will perhaps be in accord with convenience to regard that 

 portion of the entire muscle w hich springs from the fascia covering 

 the thigh as referable to the obliquus internus. 



In my account of the myology of Pipa americana, I have referred 

 to a remarkable muscle which I termed the " pectoro-mandib^dar," 

 as descriptive of its origin and insertion. I find in Xenopus under- 

 lying the mylohyoid a mass of muscle which seems to correspond 

 to this, though its insertions are different. It is, in fact, in Xenopus 

 to be regarded as a portion of the deltoid, for its fibres run alongside 

 of other fibres which arise from the clavicle and from the tip of 

 the sternum, and are inserted upon the humerus mth the rest of 

 the deltoid ; it forms, in fact, the clavicular head of the deltoid. 



The Depressor mandibulce arises, as in Rana esculenta, from the 

 fascia covering the back, and is in actual contact with the anterior 

 of the latissimus dorsi. The dorsal sheet of muscle formed by these 

 two completely covers over the underlying infraspinatus. 



The Latissimus dorsi consists not only of a portion corresponding 

 to the same muscle in the Common Frog, but of a larger posterior 



1 Clarendon Press, 1889. 



Pboc. Zool. Soc.— 1895, No. LIV. 54 



