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 | ^_ ^^^^^^^^^ ^ . p. 58 



rarely under 49 mm. .J r ^ 



(/3) Size smaller, forearm 1 ,, ^^.^^^^,. ^ . p. 83 



rarely over 44 mm. .J r ^ 



(b) rragusbroadestatcentre I pipistrellus J P' '°2 



(b) Post-calcanallobemsignificant I serotinus J P- ^30 



(B) External ear-border terminating^ i/fi^/nTrc ^ , .r^ 



under the base of the tragus .J r -r 



(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 

 (/i) Calcar extending half- | ^j t^,i,,,,, . -^ 



way from ankle to tail J -^ v j 



(b') Ears long ; when laid for- \ 



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

 yond nose-tip . . j 



(b) Posterior margin of inter- ^ ]/ fi. ,• ►.o 



femoral membrane fringed . j "^ ' ' • P* / 



2. Ears united at base — 



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



head (about 34-38 mm.) . . ( auritus j P* ^"^ 



(B) Ears of moderate length (about ] BARBASTELLA\ 



13-16 mm.) . . . .\ barbastcllus / P* ^^^ 



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



1. Size larger, forearm 50-55 mm. . . R. ferrnm-eqninum p. 228 



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



