212 BULLETIN 57, UNITED STATES NATIONAL MUSEUM. 
outer upper incisor, make it seem possible that the animal is gener- 
ically distinct from tickelli and blanfordi. The peculiarities of the 
prepuce and the presence of a large bone in the penis may indicate, 
as. supposed by Dobson, that the three species form a single group, but 
the value of these characters is not }^et well understood. 
Genus T YLON YCTERIS Peters. 
1872. Tylonycteris Peters, Monatsber. k. preuss. Akad. Wissensch., Berlin, 
p. 703. 
1878. Vesperus Dobson, Catal. Cbiropt. Brit. Mus., p. 184 (subgenus Ves- 
perugo) part. 
1898. Tylonycteris Miller, Proc. Acad. Nat. Sci. Philadelphia, p. 321, July 
25, 1898 (genus). 
Type-species. — V espertilio paehypus Temminck. 
Geographic distribution. — Malay region from Tenasserim to the 
Philippine Islands. 
Number of forms. — Only one species is now recognized. 
Characters. — Externally like a small Ep- 
tesicus with the entire head greatly broadened 
and flattened and a conspicuous fleshy pad 
on ball of thumb and sole of foot. Skull (fig. 
34) so broad that depth of brain case through 
audital bulla is barely one-half mastoid 
breadth; upper surface flat, sloping gradu- 
ally forward to nares ; rostrum very short and 
broad, its length scarcely equal to lachrymal 
breadth, its depth at front edge of orbit less 
than half breadth at same region; maxillaries 
not concealing tooth rows when viewed from 
above; a distinct blunt projection over anterior upper edge of orbit, 
perhaps representing an incipient postorbital process. Dental form- 
ula as in Eptesicus , and teeth not peculiar except in the following 
characters: Inner upper incisor conspicuously bicuspidate, its crown 
much longer than broad and nearly as long as high, the outer cusp 
projecting noticeably inward, so that the greatest width of the tooth 
is at level of its point ; upper canine with a well-developed secondary 
cusp on posterior cutting edge, unconnected with cingulum and ex- 
tending nearly to middle of main shaft. 
Species examined. — Tylonycteris paehypus (Temminck). 
Remarks. — This genus is well characterized by the remarkable flat- 
tening of the skull, a character which it shares with Mimetillus only, 
combined with the perfectly normal wing. The skull is so unusual in 
form that it appears almost as if artificially crushed. This tendency 
to widening is reproduced in the inner upper incisor, but not to any 
appreciable degree in the other teeth. 
Fig. 34.— Tylonycteris pachy- 
ptjs. Adult male. Trong, 
Lower Siam. No. 83526. xU- 
