Iviii 



IXTEKRELATIONS OF GliXERA. 



nulimciitary state : in all other Cynoptcriiie genera both m., atul m" 

 sire lodt. lu the mere dental fornnila, therefore, Bnlioni/cteris has 

 remained on a slightly more primitive stage than all other 

 Cyuopterine bats, except Mi/onycferis, but in other respects it is 

 peculiarly specialized: i^ is lost, i" shortened, m' and m, somewhat 

 reduced, some of the lower teeth (p^ and m^) subscpiarish, p^ has 

 developed an antero-external basal lobe, the ixjstorbital foramina 

 liave disajipeared, the tail is absent, the wings longer than usual 

 and marked with sharj)ly defined yellowish spots, and the general 

 size of the animal is unusually small. 



Chironax (one species) is the Javan representative of the Bornean 

 Balioin/cteris. The two genera are strikingly alike in nearh^ all 

 characters of the skull, in the general aspect of the dentition, 

 as well as in external aj)pearance, "nhile at the same time some 

 of the peculiar characters of Chironax are too important to allow 

 it to be included in Bulionycteris : — -Balioni/cteris has retained a 

 small m", in Chironax this tooth is lost ; in Balionycteris i^ is lost 

 and i" shortened, in Chironax i, is present and i'' normal in length ; 

 Balionycteris has developed an antero-external lobe in p", in 

 Chironax the lobe is represented by a well-defined cusp ; in Balio- 

 nycteris the premaxilla? are in simple contact anteriorly, in Chironax 

 ankylosed together ; and the wing-membranes of Chironax are 

 probably unspotted, i'rom this it is not ditficult to suggest the 

 characters of the common ancestor of these two genera ; it must, 

 have been a bafc very similar to Chironax, but with a small m'' and 

 the premaxillffi in simple contact; in Java it developed into 

 Chironax (m^ lost, premaxillae solidly fused), in Borneo into Balio- 

 nycteris {nf retained, i, lost, i" shortened, the antero-external cusp 

 of p^ enlarged into a lobe, wings spotted). 



The two closely interrelated monotypic genera TJtoopterus and 

 Fenthetor may be presumed to have originated from a bat similar to 

 Cynopterus, with the same number (^ — -) of incisors, the same 

 number of cheek-teeth (t : m^ and m" lost), the same length of the 

 tail, and the wing-membranes inserted on the first toe ; but the 

 raolariform teeth, particularly p^ and m,, have been unusually 

 broad, quadrate in outline, and their inner ridge very low, the upper 

 canines grooved, both upi)er and lower canines without secondary 

 cusps, there was no trace of surface cusps in any cheek-tooth, and 

 the postorbital foramina had disappeared. This form developed 

 in Western Austro-Malaya into Thoopterus : incisors unmodified, 

 jij and ra^ with large surface cusfis, tail rudimentary, wings from 

 second toe; and in Indo-Malaya into Penthetor : i, suppressed, 

 i* shortened, no surface cusps in any cheek-tooth, tail of normal 

 length, wings from first toe. 



Sphserias (one species : Burma) is probably derived from a 

 primitive " Cynopterus," i. e. a bat with the dental formula and 

 other characters essentially as in C ynoj>ter us, hnt without secondary 

 cusps in the canines and without surface cusps in the lower cheek- 

 teeth ; hut it is in certain respects more aberrant than any of the 



