1896. ] ANATOMY OF PETROGALE XANTHOPUS. 693 
Tue Muscubar System. 
Muscles of the Head and Neck. 
The Z'emporal 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 
Rodents, rises by tendon from the projecting zygomatic process of 
the maxilla and is chiefly inserted into the inflected angle 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 Sterno-mastoid runs from the front of the presternum to 
the paramastoid process. 
The Cleido-mastoid rises from the middle of the clavicle and is 
inserted just behind 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 scapular and hyoid bone; it, as well as the last 
two muscles, are supplied 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 midway 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 
gento-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; itis entirely covered by the 
trapezius, into which some of its superficial fibres are inserted. 
Macalister’ says that it rises from the first three cervical vertebra 
in Bennett’s Wallaby, and from the first two in the Great 
Kangaroo. 
1 Ann. & Mag. Nat. Hist. ser. 4, v. p. 154 (1870). 
