64 



THE OSTEOLOGY AND MYOLOGY 



foramen appears on the outside of the jaw, opposite the interspace between the first and sec- 

 ond premolars ; a third, still smaller, appears below the molar-premolar interspace. 



c. Of the Skull as a Whole. — (Fig. 9, upper, fig. 10, under, and fig. 11, lateral, view). 

 Having treated of the skull as four modified vertebrae, and of its individual bones, it 

 only remains for me to describe the whole resulting from the coherence or coalescence of 

 the numerous parts. The teeth were considered in another connection. 



Exclusive of the lower jaw, the general shape of the skull is that of an elongated cone, 

 contracted at the base, flattened below, bulging at the sides, swollen across the forehead. 



There is ndthing of 

 the pear-shaped con- 

 tour commonly seen in 

 the skulls of carnivores, 

 resulting from the ex- 

 panded brain-case. The 

 width of the cranial por- 

 tion proper is produced 

 mainly by the wide- 

 spread zygomata, and 

 the height by the sagittal crest. In consequence of the small size of the brain, in this as 

 in other marsupials, the pericephalon forms but a small proportion of the entire skull — 

 the greater part of which is appropriated to the formation of the nasal and buccal cavities, 

 and the parts accessory to the movement of the jaws. The narrowest point of the skuU 

 (excluding the zyg- 

 omata) is, in fact, 

 across the anterior 

 part of the cranium 



Fig. 9. — Skull from above. 



Fiij. 10.— Skull from below. 



proper, where the 

 hour-glass contrac- 

 tion is so great that 

 the width of the 

 cranium does not 



exceed that of the premaxillaries. The facial part of the skull is almost as long as the 

 cranial. The greatest width across the zygomata is just half the total length. The height 



varies with individ- 

 uals according to the 

 development of the 

 sagittal crest ; in 

 general it amounts 

 to about a fourth 

 of the total length. 

 The same measure- 

 ment applies to the 

 heiffht of the era- 



Fig. 11. — Lateral view of the Skull. 



nium proper and to the distance from the alveolar border to the fronto-nasal suture — the 

 depth of the upper jaw thus surpassing that of the brain-case, since fully a fourth of the 



