Affinities of " Desmalopex " and Pteralopex. 221 



border) was more developed than usual. Such is the case in 

 the Pt. pselaphon group (as well as in therelated Pt. samo'ensis 

 group), and in Pt. jjselaphon and allied species also the ante- 

 rior border (cingulura) of p^ and p'* is distinctly raised, particu- 

 larly in p^ Of the four known typical species of the pselaphon 

 group, Pt. leucopterus shows decidedly the nearest approxi- 

 mation to Pteralopex in the general aspect of the upper 

 cheek-teeth ; the crown is so much shortened as to be nearly 

 subsquarish, the anterior and posterior borders of each tooth 

 slightly but quite distinctly raised, and the "longitudinal 

 ridges'"^ more shortened and cusp-like than usual. The only 

 additional modifications required to transform an upper 

 molar of Pt. leucopterus into that of a Pteralopex is a further 

 emphasizing of the changes w'hich already have taken place 

 in the passage from a typical Pteropus molar to tliat of a 

 Pt. leucopterus, viz, a slight further shortening and broaden- 

 ing of the tooth and a much stronger development of the 

 anterior and posterior borders. The diiference in this 

 respect between P/. leucopterus smd Pteralopex is unquestion- 

 ably only one of degree. 



(12) p^, mi, and m^ modified as follows : — (a) crown 

 shortened and broadened, though not quite to the same 

 degree as iu the upper teeth : (b) inner cusp unmodified 

 (not divided), outer cusp bifid {i. e. the tip of the originally 

 simple cusp divided into two cusps by a rather deep groove, 

 which, however, is more conspicuous and goes deeper down 

 on the inner than the outer side of the ridge) : (c) posterior 

 basal ledge very strong, peculiarly oblique, being much more 

 developed on inner than outer side of teeth ; anterior basal 

 ledge undeveloped as in Pteropus generally. All characters 

 much less developed in mg than in p4 and m^. — A beginning 

 splitting of the ridges (cusps) of the lower cheek-teeth is 

 already seen in Pt. pselaphon and leucopterus (see supra) . 

 In Pt. pselaphon the character is even strongly pronounced 

 in the inner ridge of p4, very distinct also iu that of mj ; 

 in Pt. leucopterus it is distinct in the inner ridges of mj and 

 va.2, less so, or occasionally scarcely detectable, in the outer 

 ridges of the same teeth. The still stronger splitting of the 

 outer ridges of p4 and m^ oi Pteralopex is therefore only a 

 further development of the tendency already well pronounced 

 in Pt. pselaphon and leucopterus. i3ut one difference should 

 be noticed ; whenever these characters and tendencies are 

 pi'esent in the Pt. pselaphon group, they are either entirely 

 restricted to the inner cusp of the lower cheek-teeth or at 

 least more pronounced in the inner than in the outer cusp ; 

 but in Pteralopex the character is, so to say, shifted from 

 the inner cusp, which is absolutely undivided, to the outer 



