1907.] 



ANATOMY OF THE PELOBATID^. 



899 



front o£ the same muscle, in fact between it and the petrohyoideus 

 posterior secvuidus. I am not quite clear about the exact relations 

 of the corresponding parts in Lejytohrachium hasseltii. 



The petrohyoidei muscles are all four of them present in such 

 Pelobatidfe as I have dissected. The insertions of these (and of 

 the hyoid muscles generally) in Pelohates and Pelodytes have been 

 carefully figured and described by Ridewood * and compared with 

 those of liana temjyoraria. He has observed that the fourth 

 division of the petrohyoideus, i. e. the petrohyoideus posterior 

 tertius, is absent from Pelodytes. As to Rana the current figures 

 and descriptions of the hyoid musculature in R. teni2)oraria and 

 R. esGulenta indicate four petrohyoideal t muscles ; and I can 

 confirm these statements as appljdng to Rana tigrina. Farther- 

 more, it is plain from the illustrations cited below and from my own 



Text-fig. 239. 



- - A 



pyi.3. 



I 



\ 



w 



it 



• Jr-y 



LeptohrachituH hasseltii. 

 c. Points to cartilagiuous epiphj'sis of thyrohyal. p.Ji.S. Posterior petrohyoid. 



dissections, that in these species of Rana the three portions of the 

 petrohyoideus posterior are slender, of insufiicient width to come 

 into contact at their insertions on to the thyrohyal bone. It must 

 not, however, be imagined that this is distinctive of Rana. For in 

 Rana g-ap'pyi the petrohyoideus posterior is only formed of two 

 separate muscles, which are, however, broad and fanshaped and 

 nearly fill up the entire margin of the thyrohyal at their insertion. 

 The anterior of the two muscles is the larger and clearly corresponds 

 to the primus and secundus ; but in two examples of the Frog in 

 which 1 dissected these muscles I can find no evidence of the 

 fusion of two muscles. In Rana generally the three (or excep- 

 tionally two) divisions of the petrohyoideus posterior are inserted 



* P. Z. S. 1897, pi. XXXV. ligs. 10, 11. 



t E.g., Ridewood {loc. cit.) ; Wilder, Zool. Jalirb., Abth. £. Anat. ix. 1893, Taf. 20. 

 fig. 35; Haslam in Ecker's 'Anatomy of the Prog,' fig. 60, p. 65. But Goppert 

 (Morph. Jahrb.Bd.xxvi. 1898, Taf. 8. fig. 7) figures only three in Bana temporaria. 



