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Show 580 DR. W. G. RIDEWOOD ON THE HYOBRANCHIAL [May 18, of the omohyoideus. The hyoglossus in Pelodytes (hg., fig. 10) is attached to nearly the whole of the ventral surface of the thyrohyal and to the posterior part of the basal plate or body of the hyoid. As already remarked, the greater part of the ventral splint-bone lies buried in the muscle. In the Frog the area of insertion of the hyoglossal muscle (hg., fig. 11) is more restricted, and hardly extends on to the basal plate. The posterior end of the geniohyoideus internus is, in the Frog, inserted mainly into the ventral fascia of the hyoglossus, only a few stray fibres extending round this muscle to be inserted into the thyrohyal in the position marked ghi. in fig. 11. In Pelodytes the geniohyoideus internus is less bound to the hyoglossus, and its insertion into the thyrohyal (ghi, fig. 10) extends to the posterior extremity of this bone. Only two original figures of the hyoid apparatus of Pelodytes have been published. In the first, by Duges (4. pl. 3. fig. 21), the lateral foramina are shown correctly, and their presence is rightly accounted for (4. p. 56) by the union of the hyoid cornua with the antero-lateral processes ; but the dismembered parts of the hyoid arch are wanting. The ventral ossification is represented as of the form of a pair of triradiate bones. The hyoglossal sinus is not sufficiently enclosed in front, nor is the postero-lateral process of the hyoid shown of sufficient length. The second figure, by Parker (12. pl. 23. fig. 3), shows the lateral foramina, but the external enclosing cartilages are represented as in contact, and not confluent with one another. The dismembered parts of the hyoidean cornua are introduced into the figure, but they are too rod-like in shape and fail to exhibit the lamellar expansion. The hyoglossal sinus is more enclosed than in Duges's figure, and is consequently more true to nature. The ventral splint-bone, however, is triradiate and unsymmetrical, like one of those figured by Duges. The figure given by Cope (2. pl. 76. fig. 6) is admitted to be based on those of Duges and Parker, and thus calls for no special criticism. In the tendency for the processus anteriores to narrow the opening of the hyoglossal sinus, in the presence of lateral foramina, and in the dismemberment of the hyodean cornua, the hyobranchial skeleton of Pelobates very closely resembles that of Pelodytes. M y attention was directed towards this genus by Mr. Boulenger, who kindly supplied m e with specimens of Pelobates fuscus, and at the same time expressed his conviction that the hyoidean cornua were disjointed in all those genera which he includes in the family Pelobatidas (1. p. 432), and that Parker's figure of the hyobranchial skeleton of Pelobates (12. pl. 25. fig. 9) showing the hyoidean cornua continuous was incorrect. I am happy to be in a position to confirm his suspicions with regard to Parker's figure, and, as the matter is so important, I trust I may be pardoned for a slight digression here from the genus which forms the subject of this contribution. In the hyobranchial skeleton of Pelobates (fig. 12) the anterior processes are directed inwards and slightly backwards, exactly as in Pelodytes, but they do not reach the median line. The literal foramina are smaller and more pear-shaped, and in |