12 



INTRODUCTION 



constant relation to the total expanse of about .14, and varies 

 only about .02 on either side of this mean, from .13 in the long- 

 winged Noctule to .15 or .16 in the short-winged Horseshoes 

 and in the Water Bat. Another proof that in this respect 

 variation is not great is to be found in the fact that in three 

 species of about equal size, but dissimilar proportions, such as 

 the Noctule, Serotine, and Greater Horseshoe, the forearm is 

 almost of identical length. 



The proportions which the length of the forearm bears to 

 the total expanse and to the length of the head and body are 

 approximately as follows : — 



The following table shows that, of the vespertilionid bats, 

 Plecotus and Barbastella excel in length of tail, a feature combined 

 with exceptional length of lower leg and denoting a capacious 

 interfemoral membrane. The remaining species do not present 

 many differences in the former respect, but in Nyctahis 

 noctula and Pipistrellus the lower leg is shortest. The foot is 

 longest in Myotis daubentoni and JV. noctula, and shortest in 

 Barbastella. The expanse is greatest in Nyctahis, Pipist^'elluSy 

 Vespertilio, and Myotis nattere^d in the order named, and 

 least in M. daubentoni. A narrow wing is indicated in 

 Nyctalus, and less so in Vespertilio and Barbastella, by the 

 elongated third metacarpal, considerably longer in each case 

 than the fifth. The converse is the case in Pipistrelhis and 

 M. nattereri, in which the two metacarpals are about equal. 

 Barbastella appears to possess the most ample wing, every part 

 of it being exceptionally developed, although the foot is small. 



