noBsoyiA. 451 



the Eoussetine and primitive Pteropine type in no essential cha- 

 racters but the larger size of p^ and p^ and the more prominent 

 longitudinal ridges ; no well-developed posterior or antero-internal 

 basal ledges (but traces of such may be detectable), no median 

 surface ridges (one species, D. minor) : (2) a well-developed pos- 

 terior basal ledge in p\ p', p.^, and p^ ; a well-marked antero-internal 

 basal ledge or cusp in p' and p\ generally at least a trace of a 

 similar ledge in \^^ and Pj, but never in ra^ ; median surface-ridges 

 in m' and m^, sometimes also in p* and m^ (four species, D. exoleta, 

 ■pannietoisis, moluccensis, magna) : (3) essentially as foregoing, but 

 with a strong antero-internal ledge also in m^, but not in m' (two 

 species, D. peroni, smnhana) : (4) essentially as foregoing, but a 



B' 



I 



Fig. 2;').— A, B, C, D, Dohsotiia exoleta (99.10.1.4, type of species^. 

 A', B', C, D', D. viridis (7.1.1.2G1; no lower incisors). 

 A, A', upper right, B, B', lower left tooth-rows. 

 C, C, external, D, D', internal profile of p^ and ni,. 

 All figures about f (linear). 



strong antero-internal ledge also in m^ (this ledge therefore well- 

 differentiated in p% p\ m\ p.^, p,, and mj, the posterior basal ledge 

 still more strongly developed, as are generally also the surface- 

 ridges ; outer and inner longitudinal ridges of p', m', p^, and m^ 

 (or at least some of these teeth, but rarely also p' and p^) showing 

 a distinct tendency to break up into two or more separate cusps 



2g2 



