220 Mr. K. Andersen on the Characters and 



(7) Cingnlum of upper incisors very broad. As in Pt. 

 pselaphon, tuberculatus, and leucopterus. 



(8) Great enlargement of ^ combined with some reduction 

 of ij, making the contrast in the sizes of these two teeth 

 greater than in any Pterfqnis. A disproportion between ig 

 and ii is seen already in Boneia, a genus closely allied to the 

 primitive Rousettus ; the character is further developed in 

 Pteropus (which no doubt originates from a Rousettus-\We 

 form), either by an increase of ig or by this combined with 

 a reduction of ii ; and the reduction of ii culminates in the 

 complete disappearance of this tooth in Styloctenium and 

 Dobsonia (both genera allied to Pteropus). This character 

 of Pteralopex is therefore only an excessive development of 

 a tendency already present in all the related genera. The 

 numerous species of Pteropus show all intermediate stages, 

 from an ig which is only about once and a half the bulk of 

 ii, to an ig about six times the size of ii. The nearest 

 approximation to the enormous disproportion of these teeth 

 exhibited by Pteralopex is seen in the species of the Pt. 

 pselap/ion, sarnoeiisis, and lombocensis groups. 



(9) Upper cauines peculiar in the following points : — 

 (a) cingulum very strongly developed, its edge split into 

 separate tubercles ; the same is the case in Pt. pselaphon, 

 jMosus, and tuberculatus, less distinctly in Pt. leucopterus ; 

 the tubercles of the cingulum in Pt.pilosus exactly corre- 

 spond in number and position to those of Pteralopex, only 

 they are slightly smaller : [b) a strong secondary cusp half- 

 way up the hinder edge of the canine; the only species of 

 Pteropus possessing a secondary cusp in the upj.er canines is 

 Pt. tuberculatus (of the pselaphon group) ; the cusp in this 

 species is much smaller than, but similar in position to, 

 that of Pteralopex. 



(10) Cingulum of lower canines broad, forming a con- 

 spicuous shelf posteriorly. As in the Pt. pselaphon group. 



(11) p^, p^, and m' modified as follows: — [a) crown short 

 and broad, subsquarish in outline : {b) hinder (transverse) 

 border of teeth conspicuously raised, front border similarly 

 raised: (c) owing to the shortening of the teeth and the sharply 

 raised anterior and posterior borders, the usual '' longitudinal 

 ridges'' of a Pteropus molar are become much shortened (in 

 antero-posterior extent) so as to form two pointed cusps 

 situated opposite each other, the one on the labial, the 

 other on the lingual side of the tooth, a little in front of the 

 middle. The structure of the Pteralopex molar is very easily 

 derived from the molar structure of any species of Pteropus, 

 but it is most likely, of course, that it has originated from 

 a tooth in which already the posterior basal ledge (posterior 



