SKIN AND EEPRODUCTIVE OKGANS OP NOTORYCTES. 329 



large hairs of the three bundles in a group vary in size, as 

 often happens, the largest hair and gland duct is generally 

 to be found in connection with the most central bundle. 



The greatly marked glandular development of the ischio- 

 tergal region, and the peculiar structure of the ends of the 

 hairs, as described below, no doubt account for the usually 

 matted character of the hair-covering over this area. 



Structure of the Hairs. 



The ordinary hairs, both large and small, forming the fine 

 silky golden covering of Notoryctes vary considerably in 

 diameter below the epidermis as seen in the following table : 



The average size for the shaft enclosed in the skin is for 

 the large hair •040 mm., and for the small hair ^007 mm. 



In depth below the surface of the epidermis we find 

 variations according to the region ; thus over the body 

 generally a typical large hair may extend for ^49 mm. below 

 the stratum corneum, while in the "ischiotergal" patch it is 

 commonly 1'66 mm. in depth, though it may be more. 



Such difference in length may easily be found only 9 or 

 10 mm. apart. The hair roots are also very long in the head 

 region, but not so much so as in the modified patch. 



In structure [cf. 8, pp. 45, 46] the large hairs are not 

 unlike, though much smaller than, those of the Ornitho- 

 rhynchus [cf . 7 and 9] . They have a rapidly tapering 

 smooth tip (PI. 19, figs. 5 and 6). This is succeeded by a 



