222 On " Desmalo|)ex " aud Pteialopex. 



cusp. — Viewed in profile, p4, mj, and (much less so) nig of 

 Pleralopex present three cusps behind each other, viz. two 

 higher anterior (the bifid outer cusp) and a low posterior. 

 1 his latter is not a cusp peculiar to Pleralopex ; it is homo- 

 logous to the postero-external cusp arising from the posterior 

 basal ledge in all species of Pteropus which have this ledge 

 conspicuously developed. 



(13) Distribution of fur (tibia densely clothed above). 

 In all details perfectly as in the species of the Pt. pselnphon 

 and samoensis groups. 



(14) Lateral membranes arising, not from the sides of the 

 back, but from the spinal line. There is no parallel to this 

 in any known species of Pteropus (but an approximation in 

 Pt. ntelanopocjon, papuanus, 2ii\i\ neohibernicus, in which the 

 membranes arise closer together on the spinal tract than 

 in other Pteropi; the character has, however, prol)ably no 

 great taxonomic value, since Pt. papuanus and neohibernicus 

 belong to a group of species very difll'erent from that of 

 which Pt. melanopjoyon is a representative, while, on the 

 other hand, in Pt. aruensis and keyensis, though both closely 

 allied to Pt. melanopoyon, the position of the membranes is 

 perfectly normal). An exact parallel is shown by Dobsonia, 

 an aberrant genus of the Pteropus group. 



(15) Ears small, hidden in the fur, so broad above as to 

 be semicircularly rounded off. The ears are small in all 

 species of the Pt. psiluphuri and samoensis groups, often 

 hidden in the fur, but in all species more or less narrowly 

 rounded off above. In one single species of Pterojms 

 {Pt. liiingstouii) the ears are very similar in shape to those 

 of Pleralopex. 



(16) Colour of fur (blackish above and beneath). As in 

 Pt. pselaphon. 



(17) Size of animal. As an average S2)ecies of the Pt. 

 pselnphon and samoensis groups. 



Summary. — All the cranial and dental characters of Plera- 

 lopex, without any exception, point back to the species of the 

 Pt. pselaphon group, much more decidedly than to any other 

 known bats ; all external characters, except the insertion of 

 the membi'anes and the shape of the ears, {)oint in the same 

 direction. From this evidence it appears safe to assume 

 that Pleralopex (Solomon Islands) is a highly specialized 

 offshoot from that branch of Pteropus which in the Bonin 

 Islands, Pelew Islands, Vauikoro (or Mariannes), and 

 Philippines has developed into, respectively, Pt. pselaphon, 

 j)ilosus, tuberculalvs, and leucopterus, and in the Carolines 

 into Pt. insularis and phaeocephalus. Also the habitat of 

 Pleralopex is in favour of this conclusion. 



