1912] 



Taylor: A Nt w l'< rognathus 



161 



Thirty-seven specimens of Perognathus I. longimembris and 



ten of P. I. neglect us, all comparable adults, furnish the basis 

 for the diagram. As practically no dimensional differences 

 between males and females are apparent, both sexes are in- 

 cluded. 



110 120 130 140 150 160 170. 



Total length of the animal 



Fig. 1. — Correlation of variation in length of black tipping on hairs and 

 total length of individual in Peroiiiuitlius I. longimembris and Perognathus 

 I. neglectus. 



Reference to the diagram shows a general correlation lie) ween 

 large total length and short black tipping of the hair. Examina- 

 tion of the hairs with a binocular microscope disclosed two types. 

 one including spiny hairs apparently solidly pigmented for their 

 entire length ; the other, hairs with plumbeous bases, ochraceous- 



