THE FAMILIES AND GENERA OF BATS. 29 



assume, from general 'considerations of relationship, that the small 

 upper premolar is pm 3 in the Furipteridse and pm 2 in the Nyc- 

 teridse, Megadermidse, Bhinolophidse, Hipposideridse, Mystacop- 

 idse, and Molossidse. It seems probable that the degeneration of 

 pm 2 is characteristic of the fruit-eating bats and their near relatives 

 and that the reduction and disappearance of pm 3 occur in the insec- 

 tivorous groups. As regards the small upper premolars, therefore, 

 the families may be grouped as follows : 



Dominant tooth, pm * : Dominant tooth, pm * : 



Megadermidse. Pteropidse. 



Rhinolophidse. Phyllostomidse. 



Hipposideridse. Natalidse. 



Myzopodidse. Furipteridse. 



Vespertilionidse. Thyropteridaa. 

 Mystacopidse. 

 Molossidse. 



In the lower 'jaw pm 3 becomes reduced before pm 2 in all the 

 groups of Microchiroptera, some members of which possess both 

 teeth — the Khinolophidse, Phyllostomidse, Natalidse, Furipteridse, 

 Thyropteridse, Myzopodidse, and Vespertilionidse. Hence it is prob- 

 able that this is the normal process throughout the suborder. In 

 the Megachiroptera, however, the opposite is taking place. In every 

 known genus of Pteropidse both pm 2 and pm 3 are present, but pm 2 

 is invariably the smaller tooth. 



Molars. — While the posterior molar of both jaws is invariably 

 reduced, it is never absent except in certain frugivorous and sanguiv- 

 orous bats; that is, in various genera of Pteropidse and Phyllosto- 

 midse, and in all of the Desmodontidae. The middle molar dis- 

 appears in some of the Pteropidse and Desmodontidse, but is not yet 

 known to be absent in any member of the Phyllostomidse. The vari- 

 ous ways in which these teeth are suppressed are as follows : 



5 6 - Harpyionycteris, Dobsonia, Artibeus (part), Vgmpyrodes, Mesophylla, 

 5 6 7' Ariteus. 



5 6- Balionycteris, Styloctenium, Leptonycteris, Lichonycteris, Artibeus (part), 

 5 6-' Vampyriscus, Vampyressa, Chiroderma, Ectophylla, Pygoderma, Centu- 



rio, Sphseronycteris, Ametrida, Diphylla. 

 5 — Nyctymene, Oynopterus, Niadius, Thoopterus, Ptenochirus, Megserops, Sphse- 

 5 6-' Has, Scotonycteris, Epomophorus, Notopteris. 



g 



t- : Desmodus, Diazmw. 



NORMAL CUSPS. 



The typical Chiropterine dentition, which occurs essentially unmod- 

 ified in at least some genera of every family except the Pteropidse 

 and Desmodontidse, is as follows : 



Upper incisors subulate, the point slightly curved backward; cin- 

 gulum well developed, particularly on outer side; a posterior or lat- 

 eral secondary cusp usually present on one or both teeth. Lower 



