I lo VESPERTILIONID^— PIPISTRELLUS 



hind-foot 3, forearm 12, thumb 2-5, digit iii. 13, digit iv. 10, digit v. 10, 

 expanse 70. 



Proportionate lengths: — Foot, without claws, about -55 to -62 of 

 lower leg ; fifth metacarpal about equal to third ; lower leg about -30 

 to -35 of forearm, and about -25 of head and body. 



Skull: — Greatest length, 12-5; basal length in middle line, 9-5; 

 palatal length in middle line, 5 ; from posterior border of v^ to anterior 

 border of canine, 4-25 ; same in lower jaw, 5 ; greatest breadth at 

 zygoma, 8 ; posterior breadth, 6-5 ; breadth between orbits, 4 ; breadth 

 at constriction, 3-75. 



Weight in grammes : — Couch [loc. cit.) weighed 28, young and old, 

 in July, and found them varying from 2-6 to 5-4 (40 to 83 grains) : 

 Moffat {Irish Naturalist, 1900, 235) gives the weight as from 4-5 to 

 5-8 (70 to 90 grains) : while Eagle Clarke sends me the following 

 details — two males, alive, Dec, 5-53 (86 grains) and 4-63 (72 grains); 

 one, 9th May, 4-5; one, 23rd April, 4.4; one, 9th May, 4-5: females, 

 one, 8th Sept., 6-3; one, loth April, 5-15; one, 9th May, 4-5; one 

 (young), 9th Sept., 4. 



Distinguishing characteristics : — In the present state of our know- 

 ledge any small bat having an expanse less than 220 mm. may be 

 assumed to be an example of this species until proved to the contrary. 

 Its size at once distinguishes it from the British members of the genera 

 Nyctalus and Vespertilio, its ears from Plecotus, Barbnstella, and 

 RJiinolophus, leaving only Myotis, of which two species, bechsteini and 

 nattereri, are distinctly larger ; daubentoni is less so, but has distinct 

 coloration and markedly larger foot ; viystacinus is of somewhat similar 

 size, but its thirty-eight teeth, longer oval ears with their outer margins 

 terminating anteriorly about under the base of the tragus instead of 

 near the angle of the mouth, attenuated tragus, and the total absence 

 of a post-calcarial lobe, are sufficiently distinctive. On the chance of 

 P. nathusii occurring in England it would be well to remember that this 

 species has the hinder border of the wing light coloured. 



The Pipistrelle is the smallest British bat — in fact 

 the smallest British mammal — its w^eight about equal- 

 ling that of the Pigmy Shrew, which for long held 

 the reputation of being the tiniest. By the older English 

 naturalists it was confused with the Common Bat ^ of conti- 

 nental writers, a very different animal, and one having no 

 claim to be regarded as British. This error appears to 

 have originated in the days of Pennant, perhaps with Gilbert 

 White himself, but was frequently repeated until Fleming's 



^ Vespertilio mterimts, not of Linnrcus = Myotis myosotis (Bechstein). 



