OCR Text |
Show 72 MR. A. SANDERS ON THE [Jan. 6, the symphysis of the mandible, while the deeper fibres are inserted into the outer edge of the tongue. The part of this organ to which these fibres are attached is separated from the central portion by a deep furrow; this is the case on each side, so that this animal appears to have three tongues-a central one broad, fleshy and blunt, which is flanked by a pair, smaller and pointed. Hyoglossus (fig. 1, H.G.), slightly overlapped by the last, arises from the distal extremity of the thyro-hyal ; the fibres pass obliquely forward and inward, and partly join those of its fellow of the opposite side by means of a raphe ; some of the other fibres are inserted into the glosso-hyal, while the remainder pass into the lower side of the central part of the tongue, in the substance of which they pass forward to its anterior extremity. The two preceding muscles do not appear to be represented in the Iguana*. Cerato-hyoid arises from the whole length of the thyro-hyal and the segments which together form the posterior cornu of the os hyoides ; the internal and deeper fibres are inserted into the proximal end of the anterior cornu (cerato-hyal) for two thirds of its length ; the external and more superficial fibres pass on to be inserted into the side of the mandible in front and dorsad of the insertion of the neuro-mandibularis, extending forward for nearly half its length ; an additional bundle of fibres arises from the extreme distal end of the cerato-hyal to join the last-mentioned fasciculus. Whether this corresponds to the cerato-mandibular I am not sure from the memoir on Iguaua ; but on referring to the description of the myology of Chamaleon parsonii by the same authorf, I find that it does not exactly agree with any of the muscles of the throat in either of those species. Omo-hyoid (figs. 1, 2 ,& 3, O.H.) arises from the inner surface of the scapula, from aline going obliquely from the anterior to the posterior edge ; and passing forward and ventrad, its superficial fibres are inserted into the posterior edge of the basihyal, while the deeper fibres spread out and are attached to about two thirds of the distal end of the thyro-hyal and the proximal end of its second segment; the muscles of the two sides meet in a point at the middle line. There are two sterno-hyoids, as in L. belli. The one, very narrow, arises from the sternum ventrad of the sterno-mastoid, and, passing forward in front of the sterno-hyoideus profundus, is inserted into the dorsal surface of the thyro-hyal close to its articulation with the basihyal. The other, which appears to correspond to the sterno-hyoideus profundus in L. belli, although in its origin it is more superficial than the former, arises from a space on the ventral surface of the sternum left vacant by the pectorales majores, extending for about one third its length from the anterior edge of that bone. The muscles of both sides meet in a point posteriorly in the mid line ; anteriorly each spreads out into a broad and thin expansion, which is inserted into the external half of the thyro-hyal. The single sternohyoid of P.ja-ponicus X appears to correspond to the latter of the two preceding muscles. * Loc. cit. 1- P. Z. S. 1870, p. 850. \ Ibid. 1870, p. 414. |