450 DiJtiSUNIA. 



ai)d directed almost vertically downward ; in sharp profile of rostrum, 

 the tip of the incisor, very often the whole of the crown of the 

 incisor, even including the distal extremity of the premaxilla, are 

 hidden from view between the powerful anteriorly slanted canines ; 

 in conformance with the reduction of the premaxillte also the nasals 

 are conspicuously shortened, tip vertically above front or more often 

 middle (in some species even hinder edge) of alveolus of canine ; 

 diastema c-p^ much narrower than in Fteropus and llousettus. As 

 a total eflect of all these modifications, rostrum very considerably 

 shortened, from front of orbit to tip of nasals only slightly more 

 than, in certain species equal to or a little less than, breadth across 

 lower edges of lachrymal foramina. 



Other cranial characters essentially Pteropine, or with slight 

 reminiscences of the Eousettine type of skull: — Palate decidedly 

 Pteropine, narrower than in Bousetfus, particularly in the post- 

 dental portion ; occiput slightly more tubular than in llousettus, 

 bnt rather less so than in Fteropus ; tympanic ring rather broader 

 than in Fteropus, very nearly as in Itousettus ; ectopterygoid pro- 

 cesses short, as in Bousettus ; premaxillse in simple contact anteriorly 

 or slightly separated ; sagittal crest well developed. — S3 mphysis of 

 lower jaw much shorter than in Rousettus and Fteropus and sub- 

 vertically ascending ; all other characters of lower jaw perfectly 

 Pteropine : coronoid broad and ratber steeply ascending, angular 

 process broadly rounded off, condyle distinctly above level of 

 alveolar line. 



Dentition (figs. 24, 25). — ^^ ^ ^^ " "^ = 28. i, rudi- 



I2 C Pi P3 P.. '°1 ^2 ^3 



mentary, sometimes deciduous ; Pj, m^, and m'^ much reduced in 

 size. — The dentition of Dohsonia differs from that of Rousettus and 

 Fteropus chiefly in the following characters : — • 



Incisors. — Upper incisors (i'-i') small, in intercanine line, gene- 

 rally distinctly spaced ; crown chisel-shajied, the outer half (acted 

 ui)on by tip of lower canines) shorter than inner, cutting-edge 

 bilobate or irregularly crenulate. Lower incisors (i,-!.^) styliform, 

 almost functionless, closely wedged in between canines, sometimes 

 deciduous {D. viridis, crenulata). 



Gunines. — Upper canines slanted considerably forward, profile of 

 front margin of crown conspicuously convex, of hinder margi)i 

 concave ; anterior and external surfaces of crown smooth (no 

 distinct vertical groove) ; cingulum generally well developed. 

 I/Ower canines moved forward to anterior extremity of jaw, closely 

 approximated, sometimes practically in contact. 



Premolars and molars. — Tooth for tooth remarkably Pteropine, 

 in general outline and even in relative size, as well as in the degree 

 of reduction of Pj, m^, and m^ ; but p' (rudimentary in Fteropus) 

 has entirely disappeared, and the diastemas c-p^ and c-p^ are 

 narrowed. In detailed structure the premolars and molars show 

 the following four progressive stages of specialization : — 



(1) Nearly unmodified, i. e. differing (apart from loss of n^) from 



