THE FAMILIES AND GENERA OF BATS. 
179 
lower incisors are less distinctly paired, their tips curve slightly 
inward, the cutting edge of the outer is entire and distinctly longer 
than that of inner, the inner tooth is trilobate, with large median 
lobe, a minute inner lobe near tip and an equally small outer lobe 
near base, and posterior lower cheek tooth rises to a distinct cusp 
near middle. 
Species examined. — Dieemus youngi (Jentink). 
Remarks. — The peculiar short thumb with single pad a under its 
metacarpal and the slightly recurved lower incisors with their dif- 
ferent system of cusps are the principal characters which distinguish 
this genus from Desmodus. The thumb, in fact, is scarcely longer 
than in Diphylla , but it differs notably from that of the related genus 
in the presence of the large pad on metacarpal. So far as can be 
judged from the skins only, both legs and forearms share in the 
tendency to shortening so conspicuous in the thumbs. The two 
peripheral phalanges of the fingers are, however, as pointed out by 
Doctor Jentink, decidedly elongate as compared with the same bones 
in Desmodus , and this is another point of resemblance to Diplvylla. 
Genus DIPHYLLA Spix. 
1823. Diphylla Spix, Simiar. et Vespert. Brasil. Spec. Nov., p. 68. 
1878. Diphylla Dobson, Catal. Chiropt. Brit. Mus., p. 550. 
1896. Diphylla IT. Allen, Proc. U. Si- Nat. Mus., XVIII, p. 769, October, 
27, 1896. 
1896. Ewmatonycteris IT. Allen, Proc. U. S. Nat. Mus., XVIII, p. 777 
(name based on a probably abnormal specimen of Diphylla) . 
Type-species. — Diphylla eeaudata Spix. 
Geographic distribution. — Tropical America north to southern 
Mexico. 
Number of forms, — Only the type species has thus far been dis- 
covered. 
Characters. — Externally like Desmodus , but with shorter, broadly 
rounded ears, short thumb like that of Dieemus, but with no distinct 
pad under metacarpal, and a well-formed though small calcar. 
Skull differing from that of Desmodus in the much higher, broader 
interorbital region, nearly parallel-sided interpterygoid space, and 
low, weak posterior segment of mandible. Dental formula : 
-2 3 . 1 . — - 456 - - 2-2 1-1 1-1 
1 2 1 . - 2-4 5 6 -* 2 - 2 ’ C 1 ~ 2 - 2 ’ 
m 
2 - 
2 - 
Inner upper incisors as in Desmodus, but not as large, and in con- 
tact to about middle only. Outer incisor minute, structureless, barely 
if at all piercing gum, and situated close to middle of inner side of 
a The surface of this pad is crossed by a distinct furrow indicating its origin 
from the two pads of Desmodus, 
