1907.] ANATOMY OF THE PELOBATID^. 897 



that species from Megalo'phrys nasuta, the hyoid cartilage of ^Yhich 

 I have ak^eady examined and figured *. In comparing the two 

 species alleged to be of the same genus, I pointed out a difierence 

 in the curvature of the basal cartilage which happens to be of 

 morphological impoi'tance. It is most interesting to find that this 

 undoubted likeness to Pelobates, shown by Megaloplirys montana 

 but not by M. nasuta, does not occur elsewhere among the species 

 which I have had the o^Dportunity of investigating. There is a 

 very slight approach to the curvature exhibited by Megalo2}hrys 

 montana in the case of Xenophrys. But in Lpyptoh^acli'nmi the 

 processiis anteriores are directed straight forward parallel with the 

 long axis of the body of the Frog and without the slightest 

 deflection towards each other, as in Megalophrys nasuta — not the 

 first point of likeness between these two that I have pointed out 

 in the present paper. 



In describing the structure of Megalophrys nasuta, I particu- 

 larly pointed out the large size of the thyrohyals and the immense 

 mass of the investing muscles as characteristic of that Frog when 

 compared with Rana. In Rana gupjyyi, a much larger Frog than 

 Megalophrys nasuta, the thyrohyals and their investing mass of 

 muscles were absolutely considerably less in size than in the 

 Megalophrys. Furthermore, the bones and muscular sheath in 

 question are directed upwards and nearly at right angles to tlie 

 direction of the body of the hyoid. It appears to me to be justifi- 

 able to regard this position of the processes in question as some 

 evidence, though doubtless slight, in favour of considering the 

 processes as the remains of branchial arches — an homology which 

 has been disputed, and is at least not clear. As it is, the direction 

 of these thyrohyals in Megalophrys across the throat is, at any 

 rate, the direction of a bi-anchial branch. These two facts con- 

 cerning the thyrohyals and their musculature in. Megalophrys 

 apply equally well to the other species of Pelobatidee considered in 

 the present communication. They all agree in the direction of 

 these processes and in the very thick muscular covering. Pelo- 

 bates, too, agrees with its Eastern relatives entii-ely. When the 

 thyrohyals are stripped of the investing hypoglossal muscle, the 

 bony shaft is very plainly marked off from the cartilaginous 

 epiphysis, and the insertions of the petrohyoidei posteriores 

 become obvious. In all the types that I have examined the 

 thyrohyals are straight and with a " waist " in the middle. The 

 epiphysis in Megalophrys montana, Y'ik.Q that of i/.7«.aszt^a, projects 

 boot-like towards the petrous region of the skull. It differs, how- 

 ever, in some degree from the epiphysis of its alleged congener. 

 In M. nasuta the epiphysis is attached distinctly to the side — the 

 outer side — of the end of the thyrohyal. The latter bone is bony 

 up to the actual posterior truncated edge. It is, lioweA^er, carti- 

 laginous at the inner posterior corner. Thus it comes about that 

 the epiphysis is very easily detached. This is not at all the case 



* P. Z. S. 1907, p. 341, text-fig. 97. 



