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Show 1897.] SKELETON OF PELODYTES PUNCTATUS.. 579 Pelodytes are so similar to those of the Frog that no difficulty 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. Tbe impression of the ventral trunk of the in. sternohyoideus is large and of the same shape in both (sh., 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 (pal., fig. 9) which bounds the lateral foramen posteriorly. The chief difficulty in the way of the interpretation of the hyobranchial skeleton of Pelodytes is now practically overcome. The cartilage bounding the lateral foramen externally is in part the hyoidean cornu and in part a forward growth of the processus antero-lateralis-a conclusion which is supported by a study of the development (see fig. 8); while the internal boundary represents the first or proximal portion of the hyoidean cornu of the Frog-the part which 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 sternohyoideus ventralis extends relatively farther forward in Pelodytes than in Rana, but that is all. The petrohyoideus primus is in Pelodytes a smaller muscle than iu Rana. Its insertion is purely margiual in the latter genus, but in Pelodytes the muscle spreads on to the flat surface of the cartilage (p1, 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 (p2 andp3, figs. 10 and 11), but in Pelodytes the petrohyoideus tertius is inserted more posteriorly than in Rana. The fourth division of the petrohyoideus of the Frog (p)\ fig. H ) , attached to the posterior extremity of tbe thyrohyal, is absent in Pelodytes. In both genera the geniohyoideus externus is inserted into the proximal end of the processus postero-lateralis, the area of attachment of the omohyoideus (oh.) 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 constituent of the sternohyoideus (sh.', fig. 11) and a part of the geniohyoideus externus are attached. In Pelodytes, however, the sternohyoideus 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 |