1907,] ANATOMY OF THE PELOBATIB.S. 885 



sternum, and thus moi-e closely resembles the same muscle in 

 Megalojyhrys montana. 



The throat musculature of Lejitohrachium (text-fig. 232) does 

 not agree entirely with that of either of the other two genera of 

 Pelobatidse with which I am concerned in the present communi- 

 cation. I have already pointed out that in the two species of 

 Megalophrys (at any rate as commonly held) the subhyoideus is 

 a large muscle as compared with the submaxillaris. The sub- 

 hyoideus in Lej)tohrachium has exactly the same charactei'. 

 Furthermore, this species, i. e. Lei')tobracliiimi hassdtii, shows a 

 likeness to Megalophrys nasuta in the submaxillaris. I have 

 already pointed out that in Xenophrys monticola a mere seam 

 separates in the middle line of the throat the two halves of the 

 muscle. On the other hand, in both Leptohrachitmi hasseltii and 

 Megalophrys nasuta this seam is expanded into a widish tendinous 

 sheet. Megalophrys montana appears to agree with its congeners 

 in this point. Leptohrachium, however, does not agree with 

 Megalophrys in the arrangement of the submentalis muscle. 

 In the former genus, and in both species, the submentalis is com- 

 pletely concealed by the fibres of the submaxillaris, the median 

 tendinous interval ceasing some way behind the mandibular 

 symphysis. The fibres of the submaxillaris have to be cut before 

 the submentalis can be seen. The arrangement in both Lepto- 

 hrachium and Xenophrys is difierent from this, and they agree 

 entirely with each other. The submentalis is quite distinct 

 anteriorly near to the symphysis of the lower jaws, not being 

 concealed by muscular fibres of the submaxillaris. The greater 

 part of the submentalis is thus visible ; but not its insertions on 

 to each mandible. Moreover, a distinct tendinous seam on each 

 side is seen to 4ivide its fibres from those of the submaxillaris. 

 The two tendinous seams meet to form the anedian tendinous 

 interval between the right and left halves of the submaxillaris. 



So far, therefore, as concerns the superficial muscles of the 

 ventral surface, Leptohrachmm and Megalopjhrys are more nearly 

 allied than either of them is to Xenophrys. The two former 

 agree in (1) the reduced posterior pectoralis, (2) the distinctness 

 and relatively large size of the subhyoideus, (3) the considerable 

 tendinous interval between the right and left halves of the sub- 

 maxillaris. On the other hand, Leptohrachixmi and Xenophrys 

 are alike in the relations of the submentalis to the submaxillaris. 



It is interesting to compare the Eastern genera, Megalophrys., 

 Xenophrys., and LejJtohrachhmi^ Avith the essentially European 

 Pelohates *. The comparison shows an extraordinary uniformity,^ 

 so far as the muscular peculiarities already dealt with are con- 

 cerned, between Pelohates fuscus and Xenophrys monticola. The 

 pectoralis muscle is identical by reason of the large size of the 

 pectoralis posterior, which extends as far back in its origin as to the 

 posterior end of the bony style of the sternum. The muscles on 

 the floor of the mouth are also identical in the tM'o genera. It is. 

 diificult to draw any boundar}'' line between the submaxillaris 

 * This genus only extends eastward as far as Asia Minor and Syria,. 



