1907.] ANATOMY OF THE PELOBATID.E. 891 



of the semimembranosus on the ventral side of the thigh occurs 

 in Megalophrys^ LejJtohrachium, and Pelohates as well as in 

 Xeno2)hrys. 



The various facts concerning the musculature of the hind limb 

 in the Pelobatidae, which I have detailed in the foregoing pages, 

 enable us to assign certain characters to that family as a whole, 

 though the existing infoi'mation upon the Anura genei-ally does 

 not allow at present of formulating a definition of the Pelobatid^e 

 which shall diflerentiate them from other families, except possibly 

 from the Ranidfe. As opposed to the Ranidte, the Pelobatidee, so 

 far as we know them, are characterised by — (1) the appearance of 

 the distal end of the semimembranosus (at its insertion) on the 

 ventral surface of the thigh ; (2) the fusion of the sartoriits with 

 the semitendinosus, if that is to say the homologies arrived at 

 above are allowed ; (3) the fact that, the semitendinostis is either 

 a, single muscle or, if composed of more than one part (as in 

 Mexjcdophrys nasuta), the two heads arise side by side and not at 

 different levels as in Rana, and that this muscle is quite superficial 

 and not concealed by the rectus internus major or other muscles ; 

 (4) the tendon of insertion of the rectus internus major runs 

 dorsally of the tendon of insertion of the semitendinosus. 



§ Stermmi. 



The sternums of Xenophrys and Leptohrachiiim are much like 

 the sternums of Pelohates * and Megalopjhrys t. There are, 

 however, differences of detail which are worth recording as an 

 assistance towards the determination of the mutual position of 

 the various forms of Pelobatidje to which geneiic rank has been 

 given, and which are considei-ed in the present contribution to 

 the zoology of that family. I have already pointed out the great 

 differences in the proportion of the body-length to the sternum in 

 Megalophrys nasuta and Pelohates fuscus% and in the two species 

 usually referred to the genus Megalophrys §. In Xenophrys 

 monticola the total body-length from the tip of the snout to the 

 vent was 68 mm. ; from the anterior end of the omosternum to 

 the extreme end of the sternum the length was 27 mm., and the 

 true sternum measured 16 mm. In Lep)tobrachium hasseltii the 

 corresponding measurements were 55 mm., 18 mm., and 10 mm. 

 It appears, therefore, that in Xenophrys the proportions between 

 these diflerent lengths are not very different from those of 

 Megalophrys nasuta ; that is to say, the body-leng"th of Xenophrys : 

 length of entire sternum : : 10 : 4, while in Megalophrys nasuta 

 the proportions are 10 : 4*5. Again, the body-length of Xeno2}hrys : 

 length of true sternum : : 10 : 2'3, and the corresponding pro- 

 portions in Megalophrys nasuta are 10 : 2*7. Of Leptohrachium 



* Gf. Bouleiia,er, ' Tailless Batvacliia of Europe,' pt. i. p. 197, fis'. 76. 



t Beddard, P. Z. S. 1907, p. 329. 



X Id. ihid. p. cit. § Supra, p. 874. 



Proc. Zool. Soc— 1907, Ko. LX. 60 



