INTRODtJCTION. ix 



which in Megaderma (as in Pteropodidm) is perforated by a foramen 

 (Plate X. fig. 3 a ; Plate XI. fig. 2) ; in the Emhallonuridce postorbital 

 processes are scarcely developed in any of the genera except in those 

 included in the group Emballonurce, where, in most of the species, 

 they are very long, and almost circumscribe the orbit. In Mega- 

 chiroptera, however, long postorbital processes, having their bases 

 traversed by a foramen, are weU developed in nearly all the species ; 

 in the genus Pteropus, which includes the largest species of the 

 order, they reach their highest development, and in several of the 

 species there are corresponding processes from the zygomatic arches ; 

 but in Pteropus leucopterus alone is the orbital ring complete (see 

 p. 32 and Plate IV. fig. 1). 



The nasal bones vary considerably in length and form. In the 

 Megachiroptera they reach their greatest length, extending so far in 

 front that the nasal opening is small and directed forwards (Plate IV. 

 fig. 1). In Microchiroptera (except in the group Glossophagce) the 

 nasals are generally short, especially iu the leaf-nosed species of the 

 Vespertilionine alliance, where the nostrils open on the upper surface 

 of the muzzle ; in the Rhmolophid^ they are raised in a vertical 

 direction, supporting the highly developed foliaceous cutaneous 

 appendages constituting the " nose-leaf "; in the Phyllostomidce their 

 form varies most considerably — in Vampyri and Glossophagce long 

 and narrow, in Stenodermata short and broad, or deficient, as in 

 Chiroderma, where a deep fissure extends backwards between the 

 orbits (Plate XXIX. fig. 3 b), or much elevated, increasing the thick- 

 ness of the muzzle in front, as in Pygoderma (Plate XXVIII. fig. 4 b). 



The greatest difference exists in the form and size of the pre- 

 maxillary bones, in some cases even in those of species belonging to 

 the same genus. In Pteropodidce they are slender, but generally 

 united in the centre ; in Bhiixolophidce they are quite rudimentary, 

 consisting of small osseous laminae projecting forwards from the 

 nasal cartilages ; in Nycteridce they are cartilaginous in Megaderma 

 and small in Nycteris ; in aU the genera of Vesper tilionidce they con- 

 sist of slender ununited bones supported by the upper maxiUaries, 

 and separated by a wide space in front (Plate XIII. figs. 2 a, 3 j 

 Plate XrV. figs. 36, 46 ; Plate XV. figs. 56, 6 6). In those genera of 

 Emhallonuridce which approach the Vesper tilionidce nearest in general 

 structure, the premaxillary bones are also very feebly developed, and 

 in one genus (TapJiozous) they are cartilaginous, as in Megaderma ; 

 nevertheless they are less widely separated in front, and in this 

 respect lead towards the more perfectly developed premaxiUse of such 



