THE FAMILIES AND GENERA OF BATS. 
29 
assume, from general considerations of relationship, that the small 
upper premolar is pm 3 in the Furipteridae and pm 2 in the Nyc- 
teridae, Megadermidae, Rhinolophidae, Hipposideridae, Mystacop- 
idae, and Molossidae. 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 2 : 
Megadermidse. 
Rhinolophidae. 
Hipposideridae. 
Myzopodidae. 
Vespertilionidae. 
Mystacopidae. 
Molossidae. 
Dominant tooth, pm 3 : 
Pteropidae. 
Phyllostomidae. 
Natalidae. 
Furipteridae. 
Thyropteridae. 
In the lower j aw pm 3 becomes reduced before pm 2 in all the 
groups of Microchiroptera, some members of which possess both 
teeth — the Rhinolophidae, Phyllostomidae, Natalidae, Furipteridae, 
Thyropteridae, Myzopodidae, and Vespertilionidae. 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 Pteropidae 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 Pteropidae and Phyllosto- 
midae, and in all of the Desmodontidae. The middle molar dis- 
appears in some of the Pteropidae and Desmodontidae, but is not yet 
known to be absent in any member of the Phyllostomidae. The vari- 
ous ways in which these teeth are suppressed are as follows : 
5 6- Harpy ionycteris , Dobsonia, Artibeus (part), Vampyrodes, Mesophylla, 
5 6 7' Ariteus. 
5 6 - Balionycteris, Styloctenium , Leptonycteris, Lichonycteris , Artibeus (part), 
5 6-’ Vampyriscus, Vampyressa, Chiroderma, Ectophylla, Pygoderma , Centu- 
rio , Sphseronycteris, Arnetrida, Diphylla. 
5 — Nyctymene, Cynopterus, Niadius , Thoopterus , Ptenochirus , Megserops , Sphx- 
5 6-' rias, Scotonycteris, Epomophorus, Notopteris. 
Desmodus, Disemus. 
NORMAL CUSPS. 
The typical Chiropterine dentition, which occurs essentially unmod- 
ified in at least some genera of every family except the Pteropidae 
and Desmodontidae, 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 
