MUSCULAR SYSTEM OF THE RED HOWLING MONKEY 15 



actually originate on the basis mandibulae and join the rest to end on 

 the corpus. The ventromedial margin of the platysma is well defined, 

 except for some aberrant fibers which in the submental triangle inter- 

 cross with equally aberrant fascicles of the opposite side muscle. The 

 bundles directed toward the angle of the mouth run between the orbic- 

 ularis oris and buccinator under cover of a variably developed m. 

 triangularis. They end by intermixing with the fascicles of the orbicular 

 and buccinator. The fibers of the upper border of the muscle form a 

 continuous lamina with those of the zygomatico-orbital plate in the 

 zygomatic region and forward. They pick a few additional bundles 

 (m. auriculo-labiahs inferior of Huge, 1887) from the region of the 

 incisura anterior (auris). Ruge (1887) and Schreiber (1928) described 

 similar fibers in Alouatta, but the latter author did not find them in one 

 female and a very young specimen. The clavipectoral fascicles of the 

 platysma from each side advance toward the mental region. They 

 approach and eventually reach the midhne. The thyroid prominence, 

 part of the hyoid bulla, and the anterior poles of the submandibular 

 glands are seen in the area thus bound by the muscles. I could not 

 verify the distal double layering described by Schreiber (1928) in all 

 his adult specimens. M. platysma is innervated by branches of the 

 lower buccal rami of the facial nerve. 



M. occipitalis: It is a quadrilateral lamina whose fleshy fibers 

 arise from the protuberantia occipitalis externa and a httle more than 

 the medial half of the lambdoid crest (fig. 6) . They all run forward to 

 end on the dorsal border of the galea aponeurotica after covering 

 approximately the rear third of the cranial vault. The muscle is paired. 

 The two flat beUies, lying at each side of the midline, are separated 

 by a wedge-shaped and backward-pointing expansion of the galea 

 which thus reaches the protuberance. Its origin is partially covered 

 by the auricularis posterior, and the dorsal fibers of the auricularis 

 anterior et superior are seen over its lateral margin. 



M. auricularis posterior: It retains a connection with the occipi- 

 tahs, but neither of them has any with m. platysma colli et faciei 

 (fig. 6) . Origin is from the lateral half of the lambdoid crest up to the 

 point where this turns douTiward. The fleshy fibers of the muscle 

 spread out laterally forming four or five slips whose attachment is 

 on the eminentia conchae. These bundles were continuous in the right 

 side of one male mth the mm. obliqui et transversi. 



Nerve supply: The postauriculo-occipital muscles are all supplied 

 by the ramus auricularis posterior of the facial nerve. 



Mm. obliqui et transversi (m. auriculae proprius posterior of Ruge 

 (1887) and m. auricularis proprius of Schreiber (1928)): They 

 appear as transversely oriented strands joining the eminences of the 

 scapha and concha aU along the fossa anthelicis. 



