XXX PLASTIC CHAKACTEES. 



p\ and in' prominently developed, slielf-like, with raised margin, 

 the posterior ledges of the lower teeth heavy, and the cutting-edge 

 of the outer ridge of p^ and m^ distinctly (though never deeply) 

 bifid (fig. 22, p. 438). 



Again, in Dohsonia (an offshoot from the Rousetto-Pteropine 

 section) some of the modifications seen in Pteropiis are taken up 

 and further developed. In a single species {Dohsonia minor) the 

 molar structure is practically unmodified Rousettine, hut in the 

 more highly diff'erentiated forms of the genus there is a well- 

 marked posterior basal ledge in p^, p\ Pg, and p^, and a distinct 

 antero-internal basal ledge or cusp in p' and p'', often also in p^, p^, 

 m^, and m'; to these modifications are added, in the majority of 

 species, a median surface ridge (or cusp) in m' and m^, sometimes 

 also in p'' and m^, and a tendency to a splitting of both ridges of p*, 

 m\ p^, and m^ (rarely p^ and ]}') into two or more cusps (fig. 25, 

 p. 451). 



A distinct (but never very deep) splitting of the ridges of some 

 of the cheek-teeth was noted above in Pteralopex and Dohsonia. 

 The same tendency crops up in several other Fruit-bats : in 

 Pteropus pselapJwn the inner ridge of m,, and in Pleropus leuco- 

 pterus both ridges of m^ and m,^ tend to become bilobed ; in 

 ffi/psignathus the outer ridge of p^ is more or less obscurely, that 

 of m^ always distinctly trilobed or bilobed, that of m, bilobed 

 (rarely, and only as an individual anomaly, an initial stage of a 

 splitting of the outer ridge of m^, or both m^ and m', into two 

 cusps is seen in the related EpomopJiorus ) ; in Nyctimene (Cyno- 

 pterus section) the outer ridge of p^, p^, and m^ is sometimes more or 

 less conspicuously bilobed ; and, finally, in Earpyionycteris (related 

 to Dohsonia) the splitting of the ridges is more complete than in 

 any other genus of the suborder. 



The occurrence of surface cusps (or ridges) in p'', m\ m^, and m^ 

 of Dohsonia was mentioned above. Similar cusps are developed in 

 the related Harpyionycteris, and in p, and m^ of four genera of the 

 Cynopterus section, viz. Cynopterus (character not quite fixed), 

 Ptenochirus, Dyacoptemis, and Thoopterus. 



The " multicuspidate " molar structure of Earpyionycteris is 

 unquestionably the most peculiar in the suborder. In reality, 

 however, it is eff'ected simply by a combination of all the four types 

 of modification discussed above, viz. by the development of postero- 

 external and antero-internal cusps or ledges and of surface cusps, 

 and by a splitting of the ridges (see analytical description of the 

 teeth of this genus, pp. 801-803, and fig. 79, p. 802). 



Deciduousness of pV — Even when reduced to a quite rudimentary 

 (and therefore presumably almost functionless) condition p' is in 

 most genera permanent. It is known to be deciduous in a few 

 species of Ronsettus (seminudus, hrachyotis), in many species of 

 Pteropus, and in Acerodon and Styloctenium (perhaps occasionally in 

 Chironax). [It is permanently lost in Dohsonia, all Epomophorine 



