entiatcd, :it least in i, ; usunlly a faint median notch in front edge 

 of crown of i.^ ; i^ twice or twice and a half the hulk of, hut only 

 slightly higher than, ij. Lower canines generally a little shorter 

 and more recurved than upper ones, in front view more con- 

 spicuously diverging; cingulum distinct or even strong; usually a 

 well-marked vertical groove on outer face of crown. Diastema c-p^ 

 wide, subequal to antero-posterior basal diameter of upper canine. 

 Pi much reduced, once and a half or twice the bulk of, but scarcely 

 higher than, i,, permanent ; crown subcircular or somewhat elongate 

 in outline, crushing surface concave ; nearly always situated closer to 

 canine than to p^. p^, p^, and ni^ subequal in cross-section, longer 

 tlian broad ; m., smaller than m^ ; m^ much reduced, subequal to i,^, 

 outline circular or somewhat elongate. Posterior basal ledges of 

 Pj and ]\ as in corresponding upper premolars. 



A typical Pteropine dentition, similar to that described above or 

 differing only in minor details, is found in about half the number 

 of known species, viz. all forms of the Ft. Jn/ponichnnis (except 

 Ft. suhniyer), viaritninus. canleejjs, rufiis, melunotas. and melanopor/on 

 groups. 



(3) The principal modifications of the typical Pteropine dentition 

 may conveniently be epitomized under the following headings: — 



Upper incisors.— General size larger and cingulum conspicu- 

 ously broader than usual, forming a noticeable shelf posteriorly, 

 in all species of the Pt. pselaphon group, viz. Ft. pselaphon, pilosus, 

 tuberculalus, leucopterus, 'mstdaris, and phaoirphahis. (Compare 

 Fteralopex.) 



Lower incisors. — In most species i„ is about once and a half, or 

 twice, or twice and a half the bulk of ip but in some species the 

 disproportion in size is considerably greater. This is sometimes 

 due chiefly to a reduction of i,, making this tooth only about \-^ 

 of i„ : Ft. Jdiiihoceii^sis, solitarius, rodnccnsis^ and inoloxsit'iis. More 

 frequently, however, to actual enlargement of i.^, sometimes com- 

 bined with a slight reduction of i, : Ft. iiawaiettsis, mmoensb^, 

 anetiatiHS^ psel((phon, p'dosus, tuJiercidati's, and letwopterus ; in some 

 of these species i.. is about four or five times tlie bulk of i^, 

 (Compare Pteralope^v.) — In Pt. srap^datus and woodfordl all incisors 

 are reduced in size. 



Canines. — As a general rule, weak cheek-teeth (no posterior 

 basal ledges, or general size of teeth conspicuously reduced) are in 

 this genus combined with longer, slenderer, and straighter canines 

 with narrow cr even somewhat ill-dctined (but never completely 

 obsolete) cingulum, whereas heavy cheek-teeth (strong basal ledges) 

 are associated with rather shorter, stouter, and more distinctly re- 

 curved canines with strong, sharply detiiicd, shelf-like cingulum. 

 In species with very broad cingulum of the canines, the edge of the 

 cingulum sometimes shows a pronounced tendency to subdivide 

 into a row of small, round, more or less incomidetely separated 

 tubercles: Pi. sumoeni^is, andianuK, psehtphon. pilosus, I, uropientjf, 

 tubfrculatiis, iiig}dari.i, plKTocephalus (cominro with this Pfernlopex). 

 Tn Pt. liiohts.iitiHx the crown of the canines is more strong!)' com- 

 pressed fi'nm ^ide to -.idc ihnn ii^u;il. Tlic vertical gro<ive on thtj 



