MYOLOGY 



25 



/. Superficial facial musculature 



The superficial facial musculature is poorly defined in 

 the present genus, especially in Homodontomys and Neo- 

 toma. A microscopical study would bring out more of it, 

 but after a careful, gross examination, only nine of these 

 muscles were considered to be sufficiently well defined for 

 inclusion in the present work. These are as follows: 



Mm. platysma 



interscutularis 

 orbicularis oculi 

 orbicularis oris 

 buccinatorius 



auriculo labialis 

 levator labii 

 dilator naris 

 steraofascialis 



Fig. 4. Superficial facial musculature and panniculus carnosus of 

 Teonoma, 



M. platysma (fig. 4) may be considered as arising by 

 two heads. The more dorsal originates from the middorsal 

 line, extending from the occiput to the interscapular fossa. 

 It passes latero-craniad over the side of the neck and 

 joins the ventral head. The latter originates from the 

 midventral line near the manubrium and extends craniad 

 to fusion with the other head. Cranially the muscle 

 merges with the orbicularis oris upon the chin. 



In Neotoma this muscle is not so well defined, but in 

 Teonoma it is slightly more so, and stouter. 



M. interscutularis (fig. 4). Fibers which correspond 

 to this muscle are lightly indicated. They extend across 



