1897.] SKELETOIir OF PJ:L0DTTE.S PUXCTAITTS. 579 



Pelodytes are so similar to those of tLe Erog that no difficully 

 besets their determination ; but differences occur in the relative 

 sizes of certain of the muscles in the two genera, and also in the 

 extent of their surfaces of attachment. The impression of the 

 ventral trunk of the m. sternohyoideus is large and of the same 

 shape in both {sli., figs. 10 and 11). Its anterior broader end lies 

 to the outer side of the hyoglossal notch. Since it lies to the 

 inner side of the lateral foramen in Pelodytes, and is just internal 

 to the deep depression in the edge of the hyoid plate of the Frog 

 bounded anteriorly by the curving hyoidean cornu, these latter 

 spaces would appear to be homologous ; and the assumption is 

 supported by the fact that they are covered in by a membrane 

 which is perforated in both cases by the glossopharyngeal nerve 

 and the lingual branch of the carotid artery (ix., figs. 10 and 11). 

 The antero-lateral process of the Frog {pal., fig. 11), therefore, is 

 represented in Pelodytes by the cartilage {pcd., fig. 9) which 

 bounds the lateral foramen posteriorly. The chief difficulty in 

 the way of the interpretation of the byobranchial skeleton of 

 Pelodytes is now practically overcome. The cartilage bounding the 

 lateral foramen externally is in part the hyoidean coriau and in 

 part a forward growth of the processus antero-lateralis — a con- 

 clusion which is supported by a study of the deA'elopment (see 

 fig. 8) ; while the internal boundary represents the first or proximal 

 portion of the hyoidean cornu of the Frog — the part Avhich Gaupp 

 (5) calls the "manubrium" and which Parker (12) in some of 

 his figures of Anura marks " hypohyal." 



Eeturning to the muscles, the area of attachment of the sterno- 

 hyoideus ventralis extends relatively farther forward in Pelodytes 

 than in Rana, but that is all. Tlie petroliyoideus primus is in 

 Pelodytes a smaller muscle than in Pana. Its insertion is purely 

 marginal in the latter genus, but in Pelodytes the muscle spreads 

 on to the flat surface of the cartilage (p^, figs. 10 and 11). In 

 both cases the muscle lies between the processus antero-lateralis 

 and the processus postero-lateralis. The petrohyoideus secundus 

 and petrohyoideus tertius are attached to the dorso-external surface 

 of the thyrohyal bone in both genera {p^ and^^ figs. 10 and 11), 

 but in Pelodytes the petrohyoideus tertius is inserted more 

 posteriorly than in Rana. The fourth division of the petro- 

 hyoideus of the Frog (p\ fig. 11), attached to the posterior 

 extremity of the thyrohyal, is absent in Pelodytes. In both genera 

 the geniohyoideus externus is inserted into the proximal end of 

 the processus postero-latei'alis, the area of attachment of the 

 omohyoideus (o7i.) lying between those of the sternohyoideus 

 ventralis and the geniohyoideus externus. The space between the 

 thyrohyal and the processus postero-lateralis is closed by a tough 

 membrane, to the middle of which, in the Frog, the dorsal consti- 

 tuent of the sternohyoideus (s7i.', fig. 11) and a pai't of the genio^ 

 hyoideus externus are attached. In Pelodytes, however, the sterno- 

 hyoideus dorsalis is a smaller muscle (sh.', fig. 10), and it is attached 

 to the cartilage at the bottom of the sinus, close to the insertion 



