On Shell-banding as a Means of Protection. 341 
XLI.—Shell-banding as a Means of Protection. 
By A. EH. Trueman, M.Sc., University College, Nottingham, 
Autuovuen the alternate light and dark bands which charac- 
terize many animals may have some value as a protection, 
yet it must not be supposed that any protective device will 
ensure complete safety to the species which adoptsit. Thus, 
S. D. Judd * found that large numbers of insects, supposedly 
protected in various ways, were, nevertheless, detected by 
birds. W.H. Dall+ has suggested that the tendency to 
striped markings would probably aid in the concealment of 
snail-shells, although it is well known that many banded 
snail-shells (Helix nemoralis, L.) are broken at thrush 
‘anvils.” In this case, however, the value of the banding 
can be investigated with less difficulty, for a considerable 
proportion of the shells of this species are unbanded or have 
few bands. If, then, the banding is of real value in 
rendering the shells less conspicuous, the proportion of 
unbanded shells among those eaptured by birds will be 
greater than the proportion normally occurring in the same 
district. 
This problem is dealt with in an interesting paper by 
Rev. E. A. Woodruffe-Peacock t, who stated that around 
Brigg the shells occurring most commonly at thrush anvils 
were unbanded, while shells with one band came next in 
order, although these varieties were not the most abundant 
in the neighbourhood. The comparatively complex formule 
which Mr. Woodruffe-Peacock used in his work make his 
records of great value ; the less definite but quicker method 
of simply counting the bands is, however, adopted here, since 
it allows of a more convenient comparison of the broken 
shells and the standard collection. 
. Both these collections were made from the same locality— 
a belt of country on the Magnesian Limestone, some 3 miles 
long, stretching from Wollaton to Strelley, on the west of 
Nottingham. Since the Mollusca are less abundant in this 
locality than in Lincolnshire, large anvils such as those 
described in the paper referred to§$ are unknown; conse- 
quently, the records here given refer only to some two 
thousand shells. The standard collection made for com- 
parison consisted of unbleached dead shells found during the 
* * American Naturalist,’ xxxili. 1899, p. 461. 
+ See J. W. Taylor, Monog. Land and Freshwater Shells of Brit, Is, 
vol. 1. p. 95 (1894), 
t “Thrush Stones,” Naturalist, 1909, pp. 171-174 & 257-259, 
§ Loe, cit. p. 171. 
