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Show 74 MR. A. SANDERS ON THE [Jan. 6, Sterno-mastoid (figs. 1 &3, S.M.) arises from the anterior end of the articular surface between the sternum and the clavicle, and from the extremity of the cross piece of the interclavicle ; it passes forward and dorsad to be inserted into the posterior surface of the cranium, between the origins of the digastric and the complexus. Neuro-mandibularis (fig. 3, N.) in this species runs obliquely downward and forward, instead of directly downward as in L. belli and P.japonicum. It arises from the outer edge of the complexus, as in those lizards, and from the fascia of the back at the level of the scapula, and is inserted into the posterior point of the mandible. This muscle does not appear to be represented in Iguana*. Ectopterygoid is very small, and only corresponds to the internal part of the same muscle in L. belli and P. japonicum ; it is covered by the muscles of the hyoid arch, and arises from the external edge of the pterygoid, and is inserted into the inner surface of the angle of the mandible. Temporalis is a much less extensive muscle than in either P. japonicum or L. belli. It is triangular, and arises from what appears to be the squamosal and postfrontal, anterior to the quadrate ; it is inserted into the upper surface of the mandible, in front of the articulation of that bone with the quadrate. Entopterygoid (fig. 3, En.P.) i3 the principal muscle for moving the lower jaw. It arises from the posterior apophysis of the parietal, from the squamosal, and also from the anterior side of the quadrate, and is inserted into the upper edge of the mandible for about one third of its length, in front of the articulation with the quadrate. A muscle which I interpret as being homologous with the tensor tympani does not appear to be present in Iguana ; it arises from the columella, and from the anterior and upper point of the prootic, covered by both pterygoids, and is inserted into the pterygoid bone ; it was found in both P.japonicus and L. belli as well as in the present subject. Digastric (fig. 3, Di.) arises from the point where the squamosal and exoccipital meet, and descends to be inserted into the posterior end of the mandible immediately above the insertion of the neuro-mandibularis. This appears to represent the posterior part of the digastric of the human subject. The dorsal muscles appear to follow the usual arrangement. The sacro-lumbalis commences in the tail, and is partly inserted into the ilium, from which bone it takes a fresh origin. The longissimus dorsi is not distinguishable from the spinalis dorsi; they both commence in the caudal region. The complexus resembles that of L. belli; neither a trachelo-mastoid nor a transversalis colli could be found. A small muscle arises from the transverse process of the axis above the insertion of the levator scapulae, and is inserted into the basi-occipital; this differs from the rectus posticus of L. belli, and perhaps represents a rectus lateralis. Rectus anticus major resembles the same muscle in L. belli but in addition arises from the four cervical and three anterior dorsal ribs. * P. Z. S. 1867, p. 766. |
