EXTERNAL FEATURES 17 



In females this portion of the integument is barely thicker 

 than over the remainder of the animal, and seems to be with- 

 out marked glandular action. Microscopical examination 

 of vertical sections of this area shows many enlarged, highly 

 specialized glandular masses of the sebaceous type (see 

 plate 2). Some are engorged with secretion, and appear as 

 though this were accompanied by a progressive breaking 

 down of the more ental cells. They are separated by trabec- 

 ule, carrying the secretion to the external surface. It can 

 not be doubted that these highly specialized sebaceous giands 

 act as scent glands, which is perfectly apparent even to 

 human faculties. There are no suderiferous glands in any 

 of the sections examined. 



Pelage 



The body, in the genus Neotoma, is covered with hairs of 

 moderate length, without underfur, coloration is of the 

 type termed agouti in various shades of brown, and the hairs 

 of the upper surface are plumbeous at base. In Homodonto- 

 mys the hairs of the dorsal and lateral portions of the body 

 attain a length of about 15 mm., but in addition there is a 

 small proportion of overhairs, or "guard" hairs, black tipped 

 and with a length of about 20 mm. The hairs upon the head 

 are considerably shorter, in all subgenera. Upon the lateral 

 borders of the ventral surface, the hairs, now shorter, still 

 have plumbeous bases, but the tips are buffy. Midventrally 

 the hairs are buffy white, clear to the bases, except for an 

 area roughly 40 mm. in length, located centrally upon the 

 midventral line of males where the hairs are considerably 

 coarser and of a dirty brownish color. The integument of 

 this area is slightly thicker than upon the remainder of the 

 belly, and there is undoubtedly increased glandular action 

 of the skin at this point. A characteristic of this subgenus 

 is the sootiness of the dorsum of the manus and of the pes. 

 The tail is the same shade above and below, and is covered 

 with short hairs of a dark, sooty shade. 



