68 Bulletin American Museum of Natural History [Vol. XL VII 



IDIURIDJE 



The Idiuridse, recently separated from the Anomaluridse as a 

 distinct family group by Miller and Gidley, 1 are represented by three 

 quite different forms, two of which are here for the first time described. 



Idiurus Matschie 

 Idiurus Matschie, 1894, Sitzungsb. Ges. naturf. Freunde Berlin, No. 8, August, 

 pp. 194-200, 1 text-fig. Genotype, by monotypy, Idiurus zenkeri Matschie. 



Idiurus zenkeri zenkeri Matschie 

 Idiurus zenkeri Matschie, 1894, Sitzungsb. Ges. naturf. Freunde Berlin, No. 

 8, October 16, p. 197, text fig. p. 198 (animal). Type locality, Yaunde Station, 

 Cameroon District, West Africa. One specimen. 



Represented by 30 specimens (22 skins with skulls, 8 in alcohol), 

 collected as follows : 



Medje, 27 (14 d\ 13 9 ; 21 skins and skulls, 6 in alcohol), January 

 21, 25, March 9, 16, 1910. 



Avakubi, 1(9, skin and skull), January 22, 1914. 



Niapu, 2 (1 cf, 1 9 , in alcohol), January 27, 1914. 



Collectors' measurements of 19 adults (10 males, 9 females) from 

 Medje: 



Total Length Head and Body Tail Vertebrae Hind Foot Ear 



& 170 (165-175) 71 (64-78) 99 (93-104) 17.0 (16-18) 13.6 (12-14) 



9 173 (160-187) 73 (65-86) 101 (95-108) 17.3 (16-18) 13.4 (12-14) 



Measurements of 14 skulls (7 males, 7 females), from the same 

 series : 



Greatest ( =occipito-nasal) Length Zygomatic Breadth 



c? 21.0 (20.5-21.3) 12.2 (11.5-12.8) 



$ 21.4 (21.1-21.8) 12.4 (11.9-12.8) 



This fine series, particularly the 21 skins from Medje, throws much 

 light upon questions of individual, sexual, and seasonal variation. The 

 measurements, both external and cranial, indicate a slightly larger 

 average size for females than males, but there is no recognizable sexual 

 difference in coloration. 



The range of color variation is considerable in the Medje specimens 

 taken at the same date, due largely to the condition of the pelage in 

 respect to wear, the general tone of the coloration becoming darker as 

 the tips of the hairs wear off, showing more of the basal fur, while the 

 hair-tips become paler by fading. Comparison of the twelve specimens 



14 Synopsis of the supergenerie groups of Rodents.' Gerrit S. Miller, Jr., and James W. Gidley, 

 1918, Journ. Washington Acad. Sci., VIII, No. 13, July 19, p. 422. 



