20 



ANATOMY OF THE WOOD EAT 



by one of the numerous branches of the infraorbital nerve, 

 which is of large size in the present genus. It can not be 

 doubted that these vibrissae are highly sensitive and play 

 an important role in the economy of the animal. It may be 

 presumed that the longer vibrissae of Teonoma have been 

 developed to serve as a better tactile organ in the dark intri- 

 cacies of the rock slides which are frequented by that animal. 

 Anterior to the longer mystacial vibrissae are a number of 

 short ones of varying length, usually white in color. Upon 



Fig. 3. Details of cephalic vibrissal areas of Homodontomys, and show- 

 ing relative proportion of ear to head. 



the chin are a number of hairs, but slightly coarser than and 

 twice as long as the surrounding pelage, which should be 

 considered as submental vibrissae; but they can have but 

 slight function and are probably decadent. 



The superciliary vibrissae (fig. 3), situated above the eye, 

 are usually two in number, but often only one, occasionally 

 three, and in a specimen of Homodontomys, five. They may 

 be as short as 21 mm. in Neotoma, or as long as 30 mm. in 

 Homodontomys, and 45 mm. in Teonoma. 



The vibrissa which seems to correspond with the area 

 which Pocock terms the genal, but in the present animal 



