528 H. W. NORRIS AND SALLY P. HUGHES 



posterior part of the muscle (dmp.). The remamder of the hyo- 

 mandibular nerve, the ramus jugularis (jgl.) then passes poste- 

 riorly at the lateral border of the ear capsule. Posterior to the 

 latter the nerve runs slightly lateral to the vagus nerve, nearly 

 paralleling its coiu-se, and remains undivided until the level of 

 the first great sympathetic ganglion is reached (figs. 32 to 34, 

 VII). At this place the jugularis begins to divide. First to 

 be given off is a branch which runs anteroventrally into a muscle 

 that may be considered as the equivalent of the interhyoideus 

 muscle of the Urodela. Anteriorly this muscle is in contact with 

 the intermandibular muscle, but sharply distinct from it. The 

 fibers are attached at one end to the lateral border of the gonial 

 bone and at the other along the medial ventral raphe (figs. 32, 

 33, ih.). Farther posteriorly the fibers assume a more oblique 

 direction, attached anteriorly and dorsally to the longitudinal 

 tendon which runs posteriorly from the gonial, and posteriorly 

 and ventrally to the fasciae covering the underlying thoracico- 

 hyoideus muscles, and finally assuming a longitudinal direction 

 parallel with the fibers of the omo-hmiiero-maxillaris (sphincter 

 colli) muscle, with which muscle there is posteriorly an indis- 

 tinguishable blending (figs. 34, 38 to 40, sphc). As stated above, 

 the anterior part of the interhyoideus is innervated by a branch 

 of the ramus jugularis. The posterior part of the muscle is 

 supplied by other and posteriorly directed branches of the same 

 nerve. Posteriorly directed branches also innervate the omo- 

 humerc-maxillaris muscle. The latter is plainly the homologue 

 of the levator maxillae inferioris ascendens (Fischer) of Amphi- 

 uma and the sphincter colli of other urodeles and of reptiles. 

 Together with part of the interhyoideus, it constitutes an extra- 

 ordinarily elongate visceral arch muscle, extending posteriorly 

 into the trunk beyond the level of the sixth spinal nerve. Cor- 

 respondingly, there is an unusual posterior extension of the 

 branches of the ramus jugularis. 



In the larva cf Ichthyophis the ramus alveolaris VII arises 

 from the ganglion along with a mentalis internus, and not with 

 the ramus jugularis (fig. 30). In the adult it leaves the ganglion 

 as a distinct nerve. 



