656 



BALIONYCTERIS. 



base of crown ; no trace of a secondary cusp ; lower canine with 

 inner edge somewhat thickened in lower half, but not forming a 

 distinct cusp. p% p', p.,. Pj, and m^ rather broader than in Cyno- 

 ■pterus, but not nearly broadened to the same extent as in TJioopterus 

 and Fenthetor. Outer ridge of p*, in front of main cusp, developed 

 into a large basal lobe ; external profile of p' therefore an iso- 

 sceles triangle, with tip of outer main cusp nearly exactly below 

 middle of" base (in Ci/nojUerns below anterior extremity of tooth). 

 m' considerably reduced, only about half the bulk of p^ (in Cynopterus 

 usually a trifle narrower but scarcely shorter than p'). m'" rudi- 

 mentary, subequal to p'. m, conspicuously smaller than (about 

 two-thirds of, in Cynopterus subequal to) p^. m^ only one-third lo 

 one-fifth of m^, equal to or only slightly larger than p^. 



Falate-rldges. — As in Cynopterus (fig. 50, p. 591). 



External characters. — Principal differences from Cynoptcrv.s : — 

 (1) no external tail (and probably no tail vertebra: compare the 

 closelj' allied Chironax); (2) all digits much longer as compared 

 with the forearm, index of second digit 755 (in Cynopterus 668), 

 third 1847 (1637), fourth 1485 (1803), fifth 1403''(1266), but all 

 parts of the digits not lengthened to the same degree, the meta- 

 carpals by 12-17 per cent., the proximal phalanx of the third and 

 fourth digits by 19-24, that of the fifth digit by 14, the distal 

 phalanx of the third, fourth, and fifth digits only by 2-8 per cent, 

 (see table below, showing in upper row the wing-indices of BaUu- 

 uycteris calculated from measuiements of three adult individuals, 

 in lower row those of Cjinoptcrxis for comparison). — Ears small, 

 scarcely reaching hinder canthus of eye, broadly rounded oft' above ; 

 antitragal lobe small, triangularly rounded. Interfemoral un- 

 developed or extremely narrow in centre, well-developed along 

 tibia ; calcar about one-half of hind foot with claws. PoUex 

 included in membrane for its basal third or half; fascife of meso- 

 patagium as in Cynopter^is ; membranes inserted posteriorly on 

 first toe (tip of raetacaipal or base of first phalanx). Distribution 

 of far (in single sjjecies known) as in Cynopterus ; colour unusually 

 dark above ; membranes spotted ; a light spot always present on 

 front margin of ear near its base. 



Sexual differentiation. — Hair of foreneck in adult males brighter 

 in colour than, in adult females scarcely differing from, that of 

 breast and belly. 



Affinities. — In having a small m' Balionycteris is more primitive 

 than any other genus of the Cynoptcrine group, except Myonycteris. 



