192 



BULLETIN 51, UNITED STATES NATIONAL MUSEUM. 



Genus THYROPTERA Spix. 



1823. Thyroptera Spix, Simiar. et Vespert. Brasil. Sp. Nov., p. 61 (tricolor). 

 1854. Hyonycteris Lichtenstein and Petees, Monatsber. k. preuss. Akad. 



Wissensch., Berlin, p. 335 (tliscifera). 

 1865. Thyroptera Peters, Monatsber, k. preuss. Akad. Wissensch., Berlin, 



p. 580. 

 1878. Thyroptera Dobson, Catal. Chiropt Brit. Mus., p. 345. 



Type-species. — Thyroptera tricolor Spix. 



Geographic distribution. — Tropical America, north to Honduras. 



Number of forms. — Though others have been described, only two 

 species are now recognized. 



Characters. — In addition to the characters of the family the fol- 

 lowing may be mentioned. Dental formula : 



-2 3. 1. -234567 . 2j-2 1-1 

 1 2 3. 1. -2 345 6 7 * 3-3' ° 1-1 



pm 



3-3 

 3-3' 



TO 



3-3 

 3 - 3 = 



=38. 



Inner upper incisor larger than outer, but both teeth well developed, 



styliform, with small outer cusp, their 

 extremities very slender and slightly 

 curved inward, producing a faint sug- 

 gestion of the milk dentition. Lower 

 incisors 3-lobed, the outer tooth slightly 

 larger than the others. Canines weak, 

 not peculiar in structure. Premolars 

 both above and below, long, narrow, 

 moderately high, their points very 

 slender and situated at about middle 

 of crown. Third upper premolar with 

 remarkably developed inner ridge, ris- 

 ing to a cusp anteriorly nearly as high 

 as protocone of to 1 and to 2 , and show- 

 ing a slight though distinct posterior 

 cusp, the two together strongly sug- 

 gesting a protocone and hypocone. 

 First and second upper molars with 

 low but evident hypocone, the other 

 cusps with their commissures normal. Third upper molar with five 

 cusps and three well-developed commissures. Lower molar normal, 

 the outer cusps particularly high and acute. Skull (fig. 30) with 

 brain case about one and one-half times as long as rostrum, abruptly 

 elevated anteriorly, its surface smooth and rounded. Rostrum nar- 

 row, weak, and low, the upper surface nearly flat, the sides distinctly 

 inflated and translucent. Palate slightly concave laterally, nearly 

 straight longitudinally. Behind tooth rows it is abruptly narrowed, 

 and the posterior extension is parallel-sided. Basisphenoid region 

 broadly concave, the concavity bounded anteriorly by a high trans- 



Fig. 30. — Thyroptera discifera. x2f. 



