THE FAMILIES AND GENERA OF BATS, 27 



- 2 3. 1. 4 5 6 - OA „.. , „ 



12-l.-2-456- = 26 - mphylla - 



5 =26. Eomops, Molossops, (part), Cheiromeles, Molossus. 



1--. 1. -2-4567 

 -2-. 1. -2345 



.1.-2 345 6- 



-2-. 1. 45-- 



12-. 1. - 2 - 4 5 - ■ 



=24. Nyctymene. 

 20. Desmodus, Disemus. 



It will be noticed at once that certain foramlas are characteristic 

 of particular groups, or rather that a given formula never occurs in 

 widely separated families. Thus, among the genera with 34 teeth 



the formula 7—= - — ' ' ~ „ . „ „ Z is confined to the Pteropidae, 

 12- 1. -234567 r ' 



-2 3. 1. --34567. ., D , ,, + -j ,-2 3. 1. -2-4567 



12-1.-234567 t0 the ^^tormd*, and t a 8 . L _ a _ 4 6 6 7 



to the Vespertilionidse. Similarly among the 32-toothed genera the 



formula ~ „ ~ — ' ~ ~ , „ , „ is peculiar to the Embalionuridae, 

 12 3. 1. -2-4567 y 



-2 3. 1. --34567. +u Tn.ii •* -^ j-23. 1. 4 5 6 7 



12-1.-2-4^67 t0 the Ph y llostomid ^ and r23 n.-2-4567 

 to the Vesper tilionidse. The only formulas that occur in two or more 



families are 7 I j*' *' ~ !? « f I? j? 1 =38, found in the Natalidee, Thyr- 

 12 3. 1. — 234567 



_ 2 — 1 4567 



opteridse, Myzopodidse, and Vespertilionidse, ' ' — - — — — -— , - =30 



found in 9 genera of Vespertilionidse and 1 of Molossidse (Mormop- 



_o_ i 4567 



tencs), and ^— — '— - — - — ^ =28, found in two aberrant genera 



each of Vespertilionidse (Antrosous and Tomopeas) and Molossidse 

 {Molossops, part, and Mormopterus, part). Even in these excep- 

 tional cases, however, the families involved are not distantly allied. 

 The only teeth that are never absent are the canines, the last pre- 



1 t 45 



molar and the first molar, ' ..* . ~ those never present 



the first upper incisor and the first upper and lower premolar, 



-231—234567 



., „ * ' — „ „ . K „ f, . The reductions by which the various formulas 



13 3. 1. -234567 ' 



have been produced appear to be as follows : 



Incisors. — In the upper jaw the permanently missing incisor is 



without- much doubt the first. This is indicated, as shown by Winge, 



by the correspondence of the two upper teeth with the two outer of 



the lower jaw when the maximum set is present, and also, even more 



strongly, by the general tendency throughout the group for the pre- 



maxillaries to become reduced, particularly along the inner edge. 



This would inevitably result in eliminating that part of the bone in 



which the first incisor grows. Of the remaining upper incisors it is 



