PLASTIC CHARACTERS. 



the tips of the lower caiiines and somewhat altered in shape, the 

 crown being more or less obliquely bilobed. 



The normal vertical direction of the incisors is changed into a 

 strong proclirity in SjjfKerias, Syconycteris, and Harpyionyctens. 



Aberrations from the normal crowded or equidistant arrangement 

 of the incisors are seen in several genera of Maeroglossince : in 

 Melonycteris i^— i^, in XesonycUris and Xoiopteris \^—i\ and in 

 Macroglossus both i^— i' and i,— i^ are unusually widely spaced. 



In Hypsignathm {Epomophorm section) the lower incisors do not 

 bite against but close some distance in front of the upper. 



Deciduous incisors.— \' (rudimentary, barely piercing gum) is 

 deciduous in XotopteAs ; i^ (relatively well developed) otten 

 deciduous in Epomops (for details see p. 489, footnote) ; i^ (the 

 single lower incisor, almost functionless) sometimes deciduous 

 in Dobsonia {D. viridis and crenulata), perhaps so in Harpyio- 

 nyctens. 



10. Canines. 



Apart from minor variations in length and bulk, the canines may 

 be moditied : (1) by an enlargement of the cingulum, (2) by the 

 development of secondary cusps, or (3) by the development of 

 longitudinal grooves on the crown of the upper canines ; further, 

 (4)°the direction of the canines may be changed (proclivity ;_ out- 

 ward or outward-and-backward slant of lower canines), and (5) the 

 position of the lower canines may be changed. 



Ciru/ulum.—As a general rule, in Fruit-bats with weak dentition 

 the cingulum of the canines is thin or obsolescent ; on the other 

 hand, the heavier the dentition, the thicker and more prominent 

 the cingulum. In Pteropm (dentition, as a rule, unusually heavy) 

 there is a pronounced tendency to an enlargement of the cingulum, 

 particularly in the upper canines, and m certain species {Ft. 

 samoeasis and pselaphoa groups) the prominent edge of the 

 cin-ulum tends to break up into a number of small, rounded, 

 more or less incompletely separated tubercles. The extreme of 

 this tendency is seen in the related, very heavy-toothed FteraJopex, 

 in which the edge of the broad cingulum of the upper canines is 

 distinctly cuspidate. 



Secondary cusps.— ^aj be developed from the inner edge only 

 (in both upper and lower canines), or from the outer edge only (in 

 the upper canines), or from both edges (very rarely, and only 

 in the lower canines): — _ 



From inner edge only :— In Cynopteitis (fig. 48, p. o88) and the 

 closely allied Ptenochirus (fig. 51, p. 643) a distinct secondary cusp 

 is developed near the middle of the inner edge of the upper and 

 lower canines, produced by a prolongation of the cingulum. 



From outer edge only:— A small, well-marked secondary cusp 

 from the outer edge of the upper canine, above the middle of the 

 tooth, in Pteropus tubercidatus : a similar, but much larger cusp 



