804 HAEPYIONYCTERIS. 



families) had to be outlined before all the genera and species of 

 Truit-bats had been worked out in detail by the writer. 



If the extremity of the rostrum and mandible of the ffarpyio- 

 nycteris skull were covered from view, it would be difficult to point 

 out anj' cranial character of generic importance to separate it from 

 Dohsonia ; the Earpyionycteris skull is more delicately built, but 

 the general shape as well as all important details (form of brain- 

 case, form of rostrum as far forward as the tip of the nasals, form 

 of postdental palate, position of all foramina, deflection of basi- 

 cranial axis) are unmodified. The dental formula is the same in 

 both genera, except for the loss of p^ in Dohsonia ; in both one pair 

 of upper and lower iucisors (i' and i,) have been suppressed ; in 

 both the lower canines have moved forward to the extremity of the 

 jaw, so as to be quite or nearly in contact with each other and 

 leaving only a very narrow space for the rudimentary lower incisor; 

 in both the peculiar shape of the upper incisor (bifid, with inner lobe 

 longer) is essentially the same, only the inner lobe in Harpyionycterls 

 is still longer and more hook-like. The external appearance of 

 the two genera is very different indeed, but the difference is due 

 chiefly to the peculiar modification of the notopatagium of Dohsonia 

 (naked and continuous across the back); the unimportance of this 

 character for a determination of the probable affinities of a genus is 

 exemplified by Notopteris, a Fruit-bat which, though similar to 

 Dohsonia in the development of the notopatagium, is undoubtedly 

 closely related to the normal-winged Melonycteris and Nesonycteris ; 

 in the insertion of the membranes on the hind feet Harpyionycteris 

 does not differ from Dohsonia, and also the relative length of the 

 metacarpals (third longest, fourth shortest) is the same in both ; 

 curiously enough, one of the Fruit-bats which approach most closely 

 to Harpyionycteris in the shortness of the tibia is the most primitive 

 species of Dohsonia, D. minor (see p. 460) ; in many specimens of 

 Dohsonia the crown immediately in front of the ears is shaded with 

 a darker colour, and this darker tinge continued backward on the 

 occiput as a more or less distinct short median line ; a similar 

 colour pattern reoccurs in Barpyionycteris. 



The principal modifications which have taken place in the 

 development of Ilarpyioyiycteris from a Dohsonia-YiVe stock are 

 these: — The upper incisors and upper and lower canines are slanted 

 strongly forward ; the inner, hook-like lobe of the upper incisor has 

 produced a secondary cusp on the inner edge of the lower canine 

 against which it bites ; the low secondary (cingulum) cusp on the 

 external edge of the lower canine is produced by the action of the 

 powerful upper canine against this portion of the tooth : hence 

 the tricuspidate shape of the lower canine ; the secondary cusp on 

 the posterior edge of the upper canine acts against the large p, ; the 

 fusion of the premaxillje anteriorly has made the rostrum firmer. 

 In Dohsonia there is a pronounced tendency to a development of 

 antero-internal and postero- external basal ledges (cusps) in the 

 cheek-teeth, to a development of surface cusps, and to a splitting of 



