98 BULLETIN 57, UNITED STATES NATIONAL MUSEUM. 



strongly in contact at about middle; the outer placed somewhat 

 behind inner, beyond the well-developed cingulum of which they 

 scarcely extend, their terete crowns with small inner cusp; lower 

 incisors closely crowded between canines, the crown larger than high, 

 and about as broad as long, narrowed posteriorly, the upper surface 

 with distinct concavity, and dull cutting edge distinctly, though not 

 deeply, bilobed. Upper canines high and short, with distinct, though 

 not unusually developed, very oblique cingulum, but no secondary 

 cifsps, the inner surface slightly concave, with median ridge, the 

 outer surface uniformly convex; lower canines not peculiar except 

 for a slight twist in the shaft at about middle. Cheek teeth both 

 above and below essentially normal, except that the main cusps of the 

 upper molars are placed unusually far inward and the mandibular 

 molars project very noticeably beyond outer edge of jaw. Upper 

 premolar nearly parallel sided, its crown more than twice as broad as 

 long, its two cusps well developed and strongly resembling a pro- 

 tocone and paracone. Lower premolars showing no special peculiar- 

 ities, the posterior (pm 4 ) almost in contact with canine, the anterior 

 much crowded inward. First and second upper molars subequal, the 

 four cusps, three styles, and the commissures all well developed ; 

 hypocone very distinct, terete, but with scarcely a trace of commissure. 

 Posterior surface of each tooth strongly concave, so that the three 

 molars are separated by very noticeable spaces. Third upper molar 

 with about half the crown area of second, its three cones, two styles, 

 and three commissures well developed. Lower molars with all the 

 normal elements distinct. Form of skull highly characteristic ; brain 

 case deep, short oval in outline, with very prominently flaring, shelf- 

 like mastoid region and distinct sagittal crest. This divides ante- 

 riorly into two rather high ridges extending out nearly perpendicu- 

 larly and strongly downward over broadly terete interorbital region. 

 Rostrum about half as long as braincase, highly arched, the nares 

 almost tubular and opening directly forward except for a slight 

 posterior emargination. Palate distinctly concave laterally, almost 

 flat antero-posteriorly ; behind tooth rows it narrows very gradually, 

 much as in the Pteropidse. Audital bullae small, but covering about 

 half surface of cochlea;. Ears separate, slender and pointed, with 

 well-developed tragus. Muzzle pointed, the nostril pad strongly 

 projecting, but nostrils not tubular. Lips very full. Chin with well- 

 developed cross ridges. Tibia and foot together equaling about 60 

 per cent of total length. Tail well developed, considerably more than 

 half as long as femur, extending about to middle of interfemoral 

 membrane. 



Species examined.— N octilio leporinus (Linnaeus), including both 

 " leporinus " and " mastivus." 



