294 PXEROPUS PSELAPHOJT GROUP. 



spreading, everywhere more or less thickly mixed with longer, 

 coarser, paler-coloured hairs ; tibia thickly furred above. Fux 

 dark brownish above and beneath, sprinkled with paler hairs ; 

 mantle deep tawny, or dark-coloured like back. The Caroline and 

 Philippine species are in certain respects slightly aberrant. Size 

 medium or small (forearm 101-152 mm.). 



Differentiation of species. — The three typical species of this group, 

 viz. Ft. pselaphon (Bonin and Volcano Is.), pilosms (Pelew Is.), 

 and tuhcrculatus (uncertain habitat, probably either Vanikoro or 

 Mariannes), ditier from each other only in characters of minor 

 importance: details of dentition, length and colour of fur, and size. 

 The sii7gle Philippine species {Pt. leucopterus) is closely related to 

 Ft. pselaphon and pilosus, from which it differs chiefly in the 

 peculiarly shortened, subsquarish shape of the molariform teeth and 

 (probably as a consequence of this) weaker and more sloping coro- 

 noid process ; the division of the inner ridge of m^ into an anterior 

 and posterior portion, generally so well pronounced in Ft. pselap)^wn, 

 is in Ft. leucopterus fairly well marked in the same tooth and in 

 m^, sometimes also slightly indicated iu the outer ridges of these 

 teeth. The two species inhabiting the Central Carolines {Ft. insu- 

 laris and pjJiceocephalus) present most of the cranial and dental 

 characters of the group fully developed (very broad rostrum, large 

 incisors, broad cingulum of upper incisors, excessively broad 

 cingulum of canines with rim of cingulum divided into small 

 tubercles, large p^, strong posterior basal ledges of premolars), 

 but ij is not enlaiged, the cheek-teeth on the whole considerably 

 reduced in size, the coronoid jjrocess therefore weak, the tibia naked 

 above, the colour not unlike that of certain races of Ft. hypomeJamis 

 (dark above and beneath with bright mantle and pectoral patch), 

 and the size unusually small. 



Affinities of group. — Closely related to the South Polynesian 

 Pt. samoensis group. The characters of the skull are nearly identical 

 in both groups, those of the dentition similar in many important 

 points (heavy teeth, strong ledges, enlargement of i„ and Pj, &c.), 

 and the distribution of the fur the same.- — Both in skull and 

 dentition (large upper incisors, very broad cingulum of upper 

 incisors and canines, splitting of cingulum of upper canines into 

 separate tubercles, development in one species of a secondary cusp 

 in upper canines, enlargement of i^ and p^, tendency to splitting of 

 ridges of certain lower molars, shortening of all molariform teeth in 

 one species) the pselaphon group shows decidedly leanings towards 

 the highly specialized genus Pteralope.v (Solomon Islands). 



