1885.] MYOLOGY OF THE WATER-OPOSSUM. 21 



A thin sheet of muscular fibres passes from basioccipital to great 

 cornu of hyoid and pharynx, and a deeper set pass to side of tongue, 

 side of hyoid, and pliarynx. 



Constrictor muscles form one sheet. 



Scalenus posticus. — Arises by muscular fibres from third rib, 

 interdigitating with serratus magnus. It passes forwards to be in- 

 serted by a small tendon into second cervical transverse process. It 

 is closely connected with folloAving muscle. 



Scalenus anticus. — Arises from upper surface of first rib and is 

 inserted by small tendons into second to sixtli cervical transverse 

 processes. 



Traohelo-masioid. — Arises from all cervical transverse processes ; 

 inserted into mastoid just behind cleido-mastoid. Tendinous inter- 

 section at its anterior fourth. 



Complexus. — Arises from transverse processes as low as fourth 

 dorsal ; inserted into occij)ut. Tendinous intersection at its middle. 



Splenius. — Arises from S])inous processes of all cervical and first 

 two dorsal vertebrae. Inserted into occipital crest and mastoid 

 process under cover of trapezius and cleido-occipital. Its posterior 

 fibres are continuous with serratus posticus superior. 



Muscles of Trunk. 



External vhlique. — Arises by fleshy digitations from outer surfaces 

 of third to thirteenth rib. Inserted into Unea alba, tips and outer 

 border of marsupial bone, and tendon, extending from anterior 

 superior iliac spine to pubes just behind origin of pectineus. 



Internal oblique. — Very thin ventrally, thicker dorsaily. Arises 

 from lumbar fascia and anterior part of iliac crest. Inserted into 

 lower few ribs, becoming merged with lower interccstals, and into 

 outer border of marsupial bone. Tendinous intersections continue 

 the lower two ribs in this muscle for a short distance. 



Transversalis. — Consists of very thin fibres. Separated from last 

 muscle by intercostal nerves. 



Fyramidalis. — Completely overlies rectus abdominis. Arises from 

 inner border of marsupial bone by muscular fibres, and by tendinous 

 fibres from its tip. The posterior fibres pass transversely inwards 

 to linea alba, the upper fibres obliquely forwards, and those from tip 

 of marsu])ial bone directly forwards to blend with rectus. 



Rectus abdominis. — Aiises from inner border of marsupial bone. 

 Fibres pass directly forwards and are inserted into first rib close to 

 sternum, and to sternum in first intercostal space. Only one inter- 

 section was noticed situated at level of ensiform appendix. 



Sei'ratus posticus superior. — Arises by fascia from all dorsal 

 spinous processes excepting the last one. Inserted into third to 

 twelfth ribs. Its anterior fibres are connected with splenius. 



Serratus posticus inferior. — Arises by tendinous fibres from 

 eleventh to thirteenth dorsal vertebrae and from lumbar vertebrae 

 behind this. Inserted into tenth to thirteenth ribs. Its fibres overlie 

 serratus superior and are continuous behind with internal oblique. 



