46 INTRODUCTION 



maintain the numbers, and these facts form a valuable com- 

 mentary on Mr Moffat's views on the extermination by lack of 

 fertility at the outskirts of the geographical range of a species. 

 The following key to the characters of British bats will, it is 

 hoped, prove useful : — 



A KEY TO BRITISH BATS. 



I. EXTERNAL CHARACTERS: 



I. Without Nose-Leaf : — 



1. Ears separated — 



(A) External ear-border terminating under the angle of the mouth— 



(a) Post-calcarial lobe prominent — 



(a') Tragus broadest at apex . NYCTALUS p. 52 



(a) Size larger, forearm \ ^y_ ^^^^^^j^ _ . p. 58 



rarely under 49 mm. . J 

 (;8)Size smaller, forearm | ^, ^^^■^^^^^. . p. 83 



rarely over 44 mm. . J 



( PIPISTRELL, US 1 

 (b') Tragus broadest at centre I pipistrellus | P" i°3 



(b) Post-calcarial lobe insignificant | serotinus ) P" ^^° 



(B) External ear-border terminating \ j^jyOTIS . . p. 140 



under the base of the tragus . / 

 (a) Posterior margin of inter- 

 femoral membrane not 

 fringed — 



(a') Ears moderate ; when laid 

 forward not extending 

 beyond nose-tip — 

 (a) Calcar extending three- \ 



quarters way from > M. daubentoni . p. 143 

 ankle to tail . . j 



(^) Calcar extending half- \ ^_ ^ystacinus . p. 158 

 way from ankle to tail J -^ '^ •' 



(b') Ears long ; when laid for- "j 



ward extending far be- \ M.bechsteini . . p. 172 

 yond nose-tip . . J 



(B) Posterior margin of inter- | ^^_ ^^ . _ g 



femoral membrane frmged . ] r 1 



2. Ears united at base — 



(A) Ears very long, much longer than r PLECOTUS \ 



head (about 34-38 mm.) . . \ auritus ] P" " 



(B) Ears of moderate length (about ( BARBASTELLA\ ^12 



13-16 mm.) . . . .\ barbastellus | P" 



II. With Nose-Leaf , . . . . RHINOLOPHUS p. 225 



1. Size larger, forearm 50-55 mm. . . R. ferrum-equinum p. 228 



2. Size smaller, forearm 34-39 mm. . . R. hipposideros . p. 250 



