512 



PHTLLOSTOMIDiE. 



species of the frugivoroua Pteropi, otherwise so widely separated 

 from them. 



While the variability in the number and size of the premolars in 

 the Vampyri evidently depends on the length of the jaws beyond 

 the orbits, in the Stenodermata the corresponding portion of the 

 jaws having become shortened to the utmost limit apparently, the 



number of the premolars is permanently reduced to ^^ (therefore, 

 probably, the typical number in Chiroptera), and the variability in 

 the number and size of the true molars appears to be due to the 

 backward pressure of the teeth in front of the posterior molars in 

 both jaws, which prevents their growth or causes them to fall out. 



Although the Stenodermata are generally easily distinguished 

 from the Vampyri by the peculiar shortness and breadth of the 

 muzzle and by the form of the molar teeth, certain species of the 

 latter group closely resemble those of the former in external appearance, 

 agreeing almost absolutely in the form of the nose-leaf, of the ears 

 and tragus, and of the warts on the chin. These resemblances show 

 that, while the form of the teeth and jaws has become modified to 

 suit the food of the animals, the external characters, being but 

 slightly affected by this cause, have remained much the same, and 

 now indicate their common origin. 



The observations of Mr. P. H. Gosse and Mr. "W. Osbum in 

 Jamaica, tend to show that the food of these Bats is, either wholly 

 or in great part, tre6-fruit (see remarks on habits of Artiheus and 

 Stenoderma at pp. 514, 528). 



Synopsis of the Genera. 



A. Nostrils opening on the surface of a well- 

 defined nose-leaf. 

 a. Muzzle broad and very obtuse in front. 

 a'. Crowns of the molar teeth very broad, 

 their transverse exceeding their longi- 

 tudinal diameter in cross section. 

 a". Facial portion of the skull flat and 

 broad, not elevated in front. 

 a'"- Nasal opening ia the skull small, 

 not prolonged backwards ; the 

 second molar in both jaws smal- 

 ler than the first. 

 a*. Bony palate extending backwards 

 in the centre behind the last 

 molars. 

 a. Upper middle incisors broad and 

 straight; third upper molar 

 rudimentary or absent ; mo- 

 lars very broad 23. Artibeus, p. 514. 



0. Upper middle incisors conical 

 and oblique ; third upper mo- 

 lar small but distinct ; molars 

 narrower than in Artibeus . . 24. Vampyhops, p. 522, 



