86 



VESPERTILIONID^— NYCTALUS 



The foot is comparatively feeble, the post-calcarial lobe less con- 

 spicuous, and its outer margin not thickened (Plate V., p. 64). 



There are two phases of colour. In the one represented by an Irish 

 female, dated 8th September, the fur is so dark — between "olive," 

 " bistre," and " sepia " — as almost to reach " clove brown," the hair-tips 

 lighter ; in the other, represented most frequently by males in spring 

 and early summer, the hairs have a conspicuous rusty tip of almost 

 a third of their length, giving the bat a much more noctula-Yike appear- 

 ance : in this phase specimens vary between an intensified " wood 

 brown " and some shade of " mars brown." The two phases are not 

 distinctly marked off, and may intergrade ; in both, the under side is 

 lighter. The membranes, limbs, and ears are dusky, as in N. 7ioctula. 



Dr Alcock states that he sometimes, but not always, found Irish 

 males to be darker than their females, and the same remark is said to 

 apply to the young. 



Nothing is known of the processes of moult, or of a seasonal colour 

 change, but a series of four-teen examples (seven of either sex) of 

 the allied N. azorejiiii of the Azores suggests that the rusty phase 

 may represent the fading of the old winter coat in spring, and the 

 dark phase its replacement by a new pelage — a process which, as in 

 many other mammals, is characterised by much irregularity. The 

 Azorean specimens were obtained 

 by Ogilvie-Grant and N. C. Roths- 

 child between 8th March and 17th 

 May. The females are in fully 

 tinted pelage, but the males, ex- 

 cept one, are much faded, as if in 

 very old coat ; the exception, 

 killed on 17th May, appears to 

 be in process of acquiring the new 

 pelage, perhaps already donned by 

 the females. Similarly, a Rou- 

 manian male of 22nd April is in 

 rusty faded pelage. 



The skull is less than half the 

 size of that of N. noctula, its struc- 

 ture is weaker and more papery, 

 and the crests, especially the 

 sagittal, are absent or feebly de- 

 veloped (Fig. 16, No. I, p. 174). 



The teeth are similar, but 

 much smaller. The outer upper 



incisor is comparatively small, its cross-section at the base being about 

 equal to, not about double, that of the inner incisor. The anterior upper 



Fig. 7. — Front View of Incisors and 

 Canines of Nyctalns leisleri (enlarged and 

 diagrammatic). 



