112 Miller The Central American Thyroptera. 



General remarks. Of the three South American species of Thy- 

 roptera, two (T. bicolor and T. albiventer} are described as sharply 

 bicolor. brownish above and white beneath, while the third (71 

 tricolor) is said by Dobson to be reddish brown on the back and 

 pale yellowish white on the abdomen, and also to have dental 

 characters not found in the Nicaraguan animal. In Thyroptcra 

 tricolor and T. bicolor the free part of the tail equals one- fourth 

 or one-third of its whole length. In T. disci/era, on the other 

 hand, only the terminal joint and part of the penultimate joint 

 project beyond the edge of the interfemoral membrane. T. albi- 

 venter is said to have the terminal joint only of the tail free, but 

 the type specimen of this species was so mutilated that no de 

 pendence can be placed on this character. In size the four forms 

 apparently agree very closely at least it is impossible to find 

 any important differences in the measurements given in the 

 original descriptions. 



The characters of Thyroptera disci/era and of the South Ameri 

 can species as described may be thus contrasted : 



Both upper incisors bifid disci/era 



Only the inner upper incisor bifid tricolor 



Sharply bicolor, or color of back distinctly dif 

 ferent from that of belly albiventer, bicolor, tricolor 



Essentially unicolor disci/era 



One-fourth to one- third of tail free from inter- femoral 



femoral membrane tricolor, bicolor 



Only tip of tail free albiventer (?) disci/era 



The syndactylism of the third and fourth digits of the foot 

 may prove to be peculiar to Thyroptera disci/era. It is mentioned 

 by Lichtenstein and Peters in the original description of the 

 species, but none of the authors who have described South 

 American specimens make any allusion to such a condition, al 

 though in most cases they have mentioned the form of the feet 

 and claws with considerable detail. 



Another character of Thyroptera disci/era not mentioned in 

 descriptions of the South American species, but probably com 

 mon to all, is the large and conspicuous clitoris (see pi. VII). 

 In the adult female this measures 1.6 mm. in length and is about 

 half as long as the penis of a nearly full grown male. The vulva 

 opens longitudinally with the anterior commissure encroaching 

 on the basal third of the clitoris. 



