1936] Hatt, Hyraxes Collected by American Museum Congo Expedition 129 



The mammary formula of Dendrohyrax d. emini, as determined from 

 an examination of skins of 8 females from the Congo series, is 0-1 = 2, 

 which formula is typical of Dendrohyrax. 



The Pelage 

 Dichromatism 



Dichromatism in hyraxes was first noted by Aharoni 1 who observed 

 that in the Syrian species some of the individuals were light colored, 

 others dark. Shortly after this, in June, 1932, 2 MM. Heim de Balzac 

 and Begouen in the description of Heterohyrax antineae of the Hoggar 

 Plateau, Central Sahara, noted two well-marked color phases, but mis- 

 lead by an atypical combination of cranial characters they did not recog- 

 nize that one of the color phases of their supposedly new species was 

 nothing more than the earlier known Hoggar species Procavia bounhioli 

 Kollman, a slip which Schwarz 3 soon discovered. 



Dichromatism, as I have found, is also strongly marked in Dendro- 

 hyrax d. emini, a circumstance which mislead Brauer into describing too 

 many forms and Hahn into recognizing too many. The common phase 

 of the species is the type with a broad yellow wash (Plate XX, center), 

 the rarer, a dark pelage (Plate XX, right). Between these are specimens 

 superficially intermediate, but in reality these others are worn stages 

 of the light and dark types. Color and color pattern in these two sorts 

 of animals are not precisely constant, since lighter animals have, for 

 example, dirty white, light yellow or orange bellies, and some less con- 

 spicuous features show a wide range in variation. That these color 

 varieties are early established is shown by two Stage I specimens of 

 approximately equal age, both females, one taken October 22 at Avakubi, 

 the other January 21 at nearby Medje. The pelages of these two, well 

 shown in Plate XIX, differ throughout, the bases as well as the tips of 

 the hair shafts being darker in the dark individual than in the light. 

 The diffusion of the pigment extends to belly, hands and feet. 



The type specimen of D. d. emini, to judge by the color plate pub- 

 lished of it (1888, P. Z. S:, Plate ii), is an animal in the more common 

 yellow pelage. The types of D. beniensis and D. congoensis to judge by 

 the original description are individuals of emini in the darker phase. 



Well worn specimens of the light emini (Plate XXI, center) are 

 intermediate in appearance, the lighter tips to the hairs being gone, the 



1 1930, Zeitschr. fur Saugetierkunde, V, p. 330. 



2 1932, Bull. Mus. Hist. Nat. Paris, (2) IV, p. 479. 



3 1933, Ann. Mag. Nat. Hist, (10) XII, p. 625. 



