1896.] ANATOMY OP PETEOGALE XANTHOPUS. 693 



The MuscuiAH System. 

 Muscles of the Head and Neck, 



The Temporal has the usual attachments ; it rises as far back as 

 the occipital curved line and as far forwards as the level of the 

 postorbital process of the zygoma ; the two muscles of opposite 

 sides do not meet in the middle line of the head. 



The Masseter is divisible into anterior and posterior portions ; 

 the former, which corresponds to the anterior superficial part of 

 Eodents, rises by tendon from the projecting zygomatic process of 

 the maxilla and is chiefly inserted into the inflected augle of the 

 mandible ; it is not very satisfactorily separated from the posterior 

 part, which shows signs of being divided into a postero-superficial 

 and a postero-deep portion by a layer of tendon. 



The Internal Pterygoid is very large while the external is quite 

 small. 



The Sierno-mastoid runs from the front of the presternum to 

 the paramastoid jirocess. 



The Oleido-mastoid rises from the middle of the clavicle and is 

 inserted just behiud the last, with which it is unconnected ; it is 

 pierced by the spinal accessory nerve. 



The Sterno-hyoid and Thyroid are normal ; the latter has a ten- 

 dinous intersection about its middle. 



The Omo-hyoid is a flat ribbon-like muscle which has the usual 

 attachments to the scapvdar and hyoid bone ; it, as well as the last 

 two muscles, are suppUed by branches from the Ist and 2nd 

 cervical nerves direct, instead of through the medium of the hypo- 

 glossal. There is no central tendon. 



The Digastric rises from the tip of the paroccipital process and 

 is inserted into the mandible midv»ay between the angle and the 

 symphysis. There is no distinct tendon, but a small fibrous patch 

 exists above and below, about the middle. It has the usual double 

 nerve-supply. 



The Stylo-glossus is the only styloid muscle which is well marked ; 

 it rises from a tubercle on the anterior border of the paroccipital 

 process. 



The Mylo-hyoid extends almost as far forward as the symphysis. 

 There is no Transverse mandibular muscle. 



The Hyo-glossus rises from the hyoid bone and from the raphe 

 in front of it ; it lies deep to the genio-hyoid, but superficial to the 

 genio-hyo-glossus. 



The Acromio-trachelian rises from the 1st, 2nd, 3rd, and 4th cer- 

 vical transverse processes, and is inserted into the acromion and 

 outer third of the spine of the scapula ; it is entirely covered by the 

 trapezius, into which some of its superficial fibres are inserted. 

 Macalister' says that it rises from the first three cervjcal vertebra) 

 in Bennett's Wallaby, and from the first two in the Great 

 Kangaroo. 



' Ann. & Mng. Nat. Hist. ser. 4, T. p. 154 (1870). 



