483 



5. M. rectus abdominis, ... a, 3*43 oz. 



Takes its origin from the first rib and middle line of the sternum and 

 abdomen (27 inches long) ; and is inserted into the anterior surface and 

 inner edge of the Marsupial bone, of which it is the proper levator. 



K.— Muscles of Mastication, 



1. M . masseter externus, ... a, 0*44 oz. 



Arises from the outer and lower portion of the zyzomatic arch, from 

 the lower rim of the orbit and malar bone ; and is inserted into the 

 posterior fourth of the lower jaw, including the entire external 

 surface of the marsupial horizontal process. 



2. M. masseter internus et M. temporalis, . . a, . . 1 • 1 1 oz. 

 Inserted into the outer and inner surfaces of the coronoid process, and 

 into the pit on the outer side of bone. 



3. M. pterygoideus internus, . . a, 0-60 oz. 



Takes its origin from the inner side of the pterygoid plate, with some 

 fibres from the outer side, and from the fossa between it and palatal 

 plate ; and is inserted into the whole of the inner side of the marsupial 

 horizontal ramus of the lower jaw. The action of this muscle is to 

 push the cutting teeth of the lower jaw upwards and forwards against 

 the upper incisors — an action in which it is powerfully assisted by the 

 external masseter. 



Paet 2. — Opossum and Phalangeb. 



The following Tables contain the weights of the muscles of the Opos- 

 sum and Phalanger dissected by me ; and, as I have already entered 

 into so much detail with respect to the muscles of the Kangaroos, it is 

 the less necessary to specify particulars, except in the form of notes. 



A Mu 



scles of the Kip Joint. 







Opossum. 



Phalanger. 





Oz. Av. 



Grs. 



1. Psoas inagnus, 



. . o-io\ 



. . . 95 





. . 0-11 > • • • • 





. . 0*04 .... 







. . 0*12 .... 





5. „ magnus, 



. . 0-22 .... 



. . . 88 



6. ,, longus, . 





. . 44 



7. Obturator externus, . 



. . 0-09 ) 





8. „ internus, &c. 



. . 0-04 \ . . . . 



. . . 70 



9. Quadratus femoris, 



. . 0'02) 





10. Agitator cauda?, . 





< 50 



11. Glutseus maximus, 



' " (45 



12. ,, medius, . 



'. '. 0-15 .... 



' ' J 125 





. . 0 -02 .... 





. . . 20 



