NO. 1494. NOTES ON THE SLOW LEMURS-LYON. 529 



as much frosting as Cat. No. 114151, U.S.N. M., from Johore Lama. 

 Between the two extremes all intermediate conditions occnr. It 

 should l»e noted that the extremes are found in specimens from the 

 same locality and in the case of Bornean specimens taken at the same 

 time of year, one July 22 and the other August 15. The frosting is 

 also independent of age. 



The dili'erence in general coloration in the series of skins from Borneo 

 is verv striking and presents two extremes or phases, between which 

 there are all gradations. The ai:)ical color of the W00II3' hairs in the 

 dullest. Cat. No. 112337 U.S.N.M.. a very old adult male, is a little 

 lighter than Ridgway's wood brown, while the brightest colored one. 

 Cat. No. 112233 l^.S.N.M., an adult male, is a color intermediate 

 between Ridgwa3'"s ochraceous and tawny-ochraceous. It is probable 

 that the same variation would be found in series from other localities 

 were they available. The four skins from the iMalay Peninsula show 

 considerable difl'erence in color, but not such extremes as in the case 

 of the Bornean examples. 



The dorsal stripe varies considerably in extent and color. In the 

 Bornean series it runs from a rich dark brown similar to Ridgway's 

 seal brown to a color intermediate between his chestnut and russet. 

 In those specimens where it is darkest it is the best delined, while in 

 the others its borders are not so sharp. The width of the stripe varies 

 considerably. In some specimens it extends the whole length of the 

 back, narrowest posteriorh^ in others it gradually dies out along the 

 himbar i-egion. 



The head and face markings seem quite uniform in pattern, varia- 

 tions in shape and size apparently depend upon the manner of making 

 up that part of the skin. The markings are produced l)y a dou})le 

 bifurcation of the dorsal stripe on the top of the head, the posterior 

 pair of bifurcations extending to the ears and diffusing over the 

 cheeks, the anterior pair to the eyes forming a complete circle around 

 them. At the point of the doul)le bifurcation a more or less distinct 

 crown patch is seen. The color of these face-markings is in general 

 concolor with that of the dorsal stripe, but the ring immediately 

 around the eye is darker. In JVycHcehus cuicreus the face and head 

 markings are apparently absent and they are nearly so in X. concang. 



SKULL AND TEETH. 



Depending on the arrangement of the temporal ridges, the skulls of the 

 Slow Lemurs fall into two groups, (1) those in which tiie ridges event- 

 ually meet in the middle line in old age forming a sagittal crest (see 

 Plato XIII. ligs. 0-8); and (2) those in which the temporal ridges do not 

 meet in the middle line even in old age, but form two heavy lines par- 

 allel with each other, or nearly so, for a considerable distance on the 

 top of the skull. (See Plate Xlll, ligs. 1-4.) This latter condition I have 

 Proc. N. M. vol. xxxi— Of) 35 



