XIV INTBODdCTION. 



closely approaches the Phyllostomidce through Chilonyeteris) there is 

 a very imperfect joint, with a slender bony phalanx about 0"15 inch 

 long, and in JRhinopoma (as above remarked) there are two distinct 

 phalanges. In the very remarkable genus Ccelops (Rhinolophida:) 

 alone is the metacarpal bone of this finger longer than thatof the third. 



The third or middle finger is by far the longest, and, except in 

 the Phyllostomidce, has two phalanges, as in the fourth and fifth 

 fingers. In the Phyllostomidce, and in the anomalous genera Thyro- 

 ptera and Mystacina, there is a third phalanx, which evidently cor- 

 responds to the cartilaginous extremity of the second phalanx in the 

 other families of Microchiroptera ; for in some of the larger species 

 of Molossi there is an imperfect joint terminating the osseous portion 

 of the second phalanx of this finger, and in Molossus perotis (the 

 largest of that group) I have observed a distinct joint dividing this 

 bone into two. Compared with the fifth finger, this finger reaches 

 its greatest length in the Emhallonuridce and Phyllostomidce. In the 

 genera Taphozous and Biclidurus, and in the group Molossi, the me- 

 tacarpal bone equals or slightly exceeds the whole length of the fifth 

 finger. The metacarpal bone of the third finger is generally longer 

 than that of the fifth ; but in the genera Pteropus and RhinolopJms, 

 in the Nycteridm, and in many of the genera of Phyllostomidce it is 

 shorter than it. 



WhUe the metacarpal bones of the fourth and fifth fingers are 

 generally but slightly shorter, and in some cases exceed in length 

 that of the third finger, the phalanges of the same fingers vary 

 greatly in length in different families and in different species of the 

 same family. In Megachiroptera, as in the case of the other fingers 

 also, they reach their highest development, and equal, or even slightly 

 exceed, the proximal phalanx in length. In Microchiroptera they 

 are well developed in Bhinolophidce and in Nycteridce, considerably 

 shorter ia proportion to the length of the metacarpals in Phyllosto- 

 midce, and least developed in Emhallonuridce, especially in the group 

 Molossi and in the genera Taphozous and Diclidurics. In these 

 genera the terminal phalanx of the third finger is very short and its 

 distal third cartilaginous. As the antero-posterior diameter of the 

 wing depends on the length of the fourth and fifth fingers, and its 

 lateral extent on the third finger, this family is characterized by the 

 length and narrowness of the wings, which confers on the individuals 

 of each species the power of exceedingly rapid flight, contrasting re- 

 markably with the comparatively slow oar-like motion of tlie broad 

 wings of the species of Pteropodid<e. 



