110 PHYSIOLOGICAL SERIES. 



C. 94. Head of Orang-Outang (Simla satyrus) with the skin 

 removed from the left half to expose the superficial muscles. 

 These are well developed upon the face, more especially in 

 the protuberant mobile lips. They are extremely variable 

 in the details of their arrangement, and their boundaries are 

 very indistinct. This group of muscles is derived from the 

 platysma myoides and sphincter colli, it is supplied by 

 the 7th nerve, and can probably with safety be referred to 

 the hyoid portion of the superficial constrictor of the 

 Selachian. 0. C. 64 M c. Presented ly C. Dent, Esq. 



Huge, Untersuchungen liber die Gesichtsmuskulatur der 

 Primaten, Leipzig, 1887, p. 2. 



Depressor maxillae inferioris (Digastric) . 



Dobson, Trans. Linn. Soc., vol. ii. 1882, p. 259 ; Parsons, 

 Jour. Anat. & Physiol., vol. xxxii. 1898, p. 436. 



C. 95. Part of the skull of Orrdthorhynchus anatimts, showing 

 the masseter and depressor maxillae inferioris (digastric) 

 muscles. The depressor rises from the posterior border of 

 the glenoid cavity and is attached to the ventral surface of 

 the hinder part of the mandible. It is doubtful whether 

 this muscle is homologous with the depressor of other 

 mammals, in spite of its somewhat analogous position and 

 action. 



C. 96. Skull of Potorous [Hypsiprymmis] tridactylus, with the 

 depressor maxilla? inferioris (digastric) and mylohyoid 

 muscles. The depressor is indistinctly digastric, the anterior 

 and posterior bellies being separated from one another by 

 a slight constriction and tendinous intersection. A few 

 tendinous fibres pass from the intersection to the posterior 

 margin of the mylohyoid. The anterior belly is attached 

 to the mandible near the syrnphysis. 



C. 97. Head of a young Three-toed Sloth (Bradypus tridac tyhis) 

 showing the chief muscles of mastication. The two bellies 

 of the depressor maxillse inferioris (digastric) are separated 



