NYCTINOMUS TENUIS. 



The neck is of moderate length, and robust; and the body is broader at the thorax, 

 and gradually attenuated towards the posterior extremities. It is densely covered with 

 a very deUcate fur, which also forms a regular border along the sides, from the 

 shoulders to the vent. The breasts and sexual organs are completely hid from view 

 by the close hairy covering. The expansion of the wings is comparatively greater 

 than in the other Vespertilionidte. The bones of the arms, and the phalanges being 

 greatly lengthened and very slender, the form of the wings is consequently narrow, 

 oblong, and sharp towards the extremity. This indeed is the general character of 

 the Nyctinomi ; but it exists in a greater degree than in the species from Egypt and 

 Bengal, and from this character the specific name is derived. The Nyctinomus 

 tenuis is also pecuharly distinguished by the narrowness of the membrane of the 

 wings near the body, opposite to the junction of the arm and fore-arm, from another 

 Javanese species contained in our collections, which I have denominated Nyctinomus 

 dilatatus, the characters of which I shall concisely define at the end of this. article. 



The lower extremity of the os humeri is provided at its articulation, with a 

 cartilaginous appendage of an irregular form, from which a very dehcate tendon 

 passes, parallel to the arm, towards the shoulder. The thumb, comparatively with 

 other Nyctinomi, is long, and provided as usual with several bones for its support ; 

 the claw is very minute. The index has three phalanges, of which the two exterior 

 are scarcely distinguishable by the naked eye. The middle finger has four, and each 

 of the others three phalanges : the extreme ones are very slender and delicate. The 

 membrane is delicate, transparent, and dotted on each side of the body towards the 

 arms, exhibiting a character wliich exists in a certain degree perhaps in aU Nyctinomi, 

 and which has suggested the name of acetabulosus for Commerson's species ; it passes 

 over the carpus to unite itself with the interfemoral membrane. The latter is consi- 

 derably tapering in the middle ; having several deep folds near the posterior border, 

 and being provided with several bundles of muscular fibres stretching transversely 

 over it. 



The tail is long, slender, and extremely delicate at the extremity; of about 

 nine cyhndrical vertebrae which compose it, three only are enveloped in the mem- 

 brane : more than one half of this organ is thus detached. The feet are provided 

 with five toes of nearly equal length, each of which has a strongly compressed and 

 sharp claw : numerous strong bristly hairs are scattered on the feet, spreading irre- 

 gularly in all directions. 



The colour of the transparent membrane of the wings is sooty black, with a 

 slight tint of brown : it is more intense in the ears, the nose, the tail, and the inter- 



