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Show 1870.] ON THE MYOLOGY OF PLATYDACTYLUS JAPONICUS. 413 6. Notes on the Myology oi Platydactylus japonicus. B y A L F R E D S A N D E R S , M.R.C.S., F.Z.S. If one may judge from treatises on Comparative Anatomy recently published, the muscles of the Lacertilia do not appear to have received a great deal of attention. This consideration has emboldened me to lay tbe following notes on the myology of Platydactylus japonicus before the Zoological Society,-the more so as this species differs considerably in the arrangement of its muscular system from the Iguana tuberculata, the myology of which was described in a paper by Mr. St. George Mivart, published in the Society's Proceedings in 1867. Hyo-mandibular.-On the ventral aspect of the throat are seen two superficial skin-muscles, the most anterior of which arises by means of a tendinous raphe covering the glosso-hyal, being thus united to its fellow of the opposite side; and passing directly outwards through the fibres of the mylo-hyoid, it is inserted into the supplementary or coronoid and opercular pieces of the mandible immediately beneath the posterior teeth. The next muscle slightly overlaps the last anteriorly, and arises from the basihyal at the point where the anterior horns are given off, and from a thin aponeurosis over the hyomandibular, and also from one covering the trachea behind the same point. As far back as opposite the posterior end of the mandible it is divisible into three distinct portions; the posterior passes outwards and upwards, and spreads out into a thin layer, which is inserted into the superficial fascia at the back of the head, intimately connected with the trapezius. The anterior portion forms a thin layer, covering the external pterygoid, and is inserted into the supraangular piece of the mandible; its posterior fibres are collected into a thicker mass, which passes upwards and rather backwards behind the mandible, and is inserted into the aponeurosis of the side of the neck and the complexus. The middle portion passes upwards within the mandible, and is inserted into the extremity of the terminal segment of the anterior cornu (cerato-hyal) of the os hyoides, close to the attachment of the latter to the exoccipital. This latter part perhaps represents stylo-hyoid. Mylo-hyoid arises from the body of os hyoides (basihyal) and from the posterior cornu (thyro-hyal) as far outwards as the external pterygoid, leaving a space through which that muscle passes. The fibres run forward, and are inserted into the whole length of the dentary piece of the mandible, with the exception of a small portion anteriorly close to the symphysis; it is also attached to the fascia covering the anterior point of the glosso-hyal; it is situated deeper than or above the preceding muscular layers. Genio-hyo-glossus arises from the posterior cornu of the os hyoides just beyond its articulation with the basihyal; and passing forward, its superficial fibres are inserted into the symphysis of the mandible, while the deeper ones go to the side and back of the tongue ; tbe PROC. ZOOL. Soc-1870, No. XXVIII. |
