252 BULLETIN 51, UNITED STATES NATIONAL MUSEUM. 
not forming noticeable secondary cusps, except occasionally at pos- 
terior base of lower tooth. First upper premolar (pm -) minute but 
perfectly in tooth row and not specially crowded. Second upper pre- 
molar (pm 4 ) not in contact with canine, well developed, and with 
large antero-internal cusp. Lower premolars normal in form and 
size, the first not as high as second, but with the cross section nearly 
as great. Molars normal ; m 1 and m 2 with inner segment large, the 
terete hypocone unusually distinct ; m 3 with crown area more than 
half as great as that of m 1 or m 2 and about equal to that of pm 4 ; 
the metacone and three commissures well developed. Lower molars 
with all the cusps normal in size and form, the three inner approxi- 
mately equal in height. Skull (figs. 41-43) with rounded or some- 
Fig. 41.— Nyctinomus brasiliensis. Fig. 42.— Nyctinomus europs. Adult fe- 
Parana, Brazil. No. 37878. x 2. male. Brazil. Paratype, No. 101502. x 2£. 
what flattened, moderately wide brain case about one and one-tliird 
times as long as rostrum, above level of which it is very slightly ele- 
vated, and at least half as deep as wide; a distinct depression in 
front of occipital region ; sagittal crest scarcely indicated ; lachrymal 
and supraorbital ridges low but evident; dorsal surface of rostrum 
with faint longitudinal concavity between orbits; zygoma slightly 
expanded at middle. Anterior palatal emargination about as large 
as base of canine, wider posteriorly than between incisors; palate 
slightly arched, but nearly flat antero-posteriorly ; pterygoids paral- 
lel ; basisphenoid pits moderately developed or obsolete. Ears large 
arid rounded, arising from same point on forehead. Laid forward 
they extend distinctly beyond extremity of muzzle ; anterior border 
of ear conch with 6 to 8 horny excrescences ; keel well developed : 
tragus small, flattened, squarely truncate above; antitragus variable 
