Page:Notes on the Slow Lemurs.pdf/3

. as much frosting as Cat. No. 114151, U. S. N. M., from Johore Lama. Between the two extremes all intermediate conditions occur. It should be 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 difference in general coloration in the series of skins from Borneo is very striking and presents two extremes or phases, between which there are all gradations. The apical color of the woolly hairs in the dullest, Cat. No. 142237, 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. 142233, U. S. N. M., an adult male, is a color intermediate between Ridgway’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 Malay Peninsula show considerable difference 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 defined, 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 posteriorly, in others it gradually dies out along the lumbar region.

The head and face markings seem quite uniform in pattern, variations in shape and size apparently depend upon the manner of making up that part of the skin. The markings are produced by a double 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 double 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 Nycticebus cinereus the face and the head markings are apparently absent and they are nearly so in N. coucang.

Depending on the arrangement of the temporal ridges, the skulls of the Slow Lemurs fall into two groups, (1) those in which the ridges eventually meet in the middle line in old age forming a sagittal crest (see Plate XIII, figs. 5–8); and (2) those in which the temporal ridges do not meet in the middle line even in old age, but form two heavy lines parallel with each other, or nearly so, for a considerable distance on the top of the skull. (See Plate XIII, figs. 1–4.) This latter condition I have 2em