NYCTICEBUS 23 



procured, but its range is unknown ; while in the Island of Banka, to 

 the east of Sumatra, N. bancanus was procured. In Java N. javani- 

 cus is a resident, while N. borneanus represents the genus in Borneo. 

 On Bungaron Island of the Natuna Group, N. natun^e was discovered, 

 and from somewhere in the Philippine Archipelago, locality unknown, 

 N. menagensis was brought. In coloration these animals differ con- 

 siderably even among members of the same species, and the hue of the 

 dorsal stripe, usually a very conspicuous marking, varies greatly both 

 in color and extent. Some animals have a conspicuous spot on the 

 crown of the head, others are without this, and the presence or absence 

 of this coloration has been utilized for arranging the different forms 

 into two groups. The manner in which the temporal ridges approxi- 

 mate and form a sagittal crest has served also for the arrangements 

 into groups of the known forms, and each method has answered fairly 

 well, although in a non adult animal the skulls fail to indicate whether 

 the temporal ridges will, in the fully mature individual, produce by 

 joining together, a sagittal crest or not. The number of upper incisors 

 varies between two and four, and it is difficult to determine from lack 

 of material, the exact reason for this, whether it is an individual 

 peculiarity, or a character of scientific importance. At the present 

 time this question cannot be satisfactorily answered, but it would seem 

 that, from such evidence as we have, the major portion would indicate 

 individual variation, caused however neither by age nor sex. 



KEY TO THE SPECIES. 



A. Skulls with sagittal crest ; incisors two. 



a. Lower orbital ring broad; under parts whitish. .N. borneanus. 



b. Lower orbital ring narrow ; under parts buffy. . . .N. bancanus. 



B. Skulls without sagittal crests ; incisors four. 



a. Stripe on forehead bifurcating and encircling 



the eyes N. tenasserimensis. 



b. Stripe on forehead not bifurcating nor en- 



circling the eyes. 



a.' Lines on head indistinct N. coucang. 



b.' Lines on head absent iV. c. cinereus. 



c.' Lines on head conspicuous. 



a." Dorsal stripe in a reddish white or 

 silvery white area. 



a."' Hands and feet reddish N. javanicus. 



b."' Hands and feet dusky N. natuna. 



