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. — Dicemvs youngi (Jentink). 



Remarks. — The peculiar short thumb with single pad " under its 

 metacarpal and the slight!}*- 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 difl'ers 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 Diphylla. 



Genus DIPHYLLA Spix. 



1823. Diphylla Spix, Simiar. et Vespert. Brasil. Spec. Nov., p. 68. 



1878. Diphylla Dobson, Catal. Ohiropt Brit. Mus., p. 550. 



1896. Diphylla H. Allen, Proc. U. S. Nat. Mus., XVIII, p. 769, October, 



27, 1896. 

 1896. Ha-matonycterls H. Allen, Proc. U. .S. Nat. Mus., XVIII, p. 777 



(name based on a probably abnormal specimen of Diphylla). 



Type-species. — Diphylla ecaudata 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 Dhvmus, 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 : 



-23.1. 456-- 2-2 1-1 1-1 2-2 ofl 



12-. 1. -2-4 5 6- 2-2' 1-2' 7 2-2' 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 



" The surface of this pad is crossed by a distinct furrow indicating its origin 

 from the two pads of Desmodus. 



