9014 Mollusks. 
in the accounts we have of the four localities presenting these remark- 
able perforations: first, that in all the instances the perforated rocks 
are calcareous—a limestone; secondly, that the excavations are never 
on the upper surface of the rocks, as would be the case were they the 
effect of weather, but are either inwards from the edge, or upwards 
from the under surface of projecting ledges; thirdly, that such 
positions offer protection to the snails from the weather, which 
habitations on the upper surface of the rock would not; fourthly, that 
the channels are always described as of considerable depth, of un- 
equal diameter in different parts, as tortuous, and as frequently con- 
fluent; ji/thly, that they are tenanted by Helix hortensis, which is 
presumed to be the excavator. 
This last statement requires some explanation: M. Bouchiatd: 
Chatereaux tells us that the boring-snail of the Bois-des-Roches is 
Helix hortensis: Dr. Buckland states that the Tenby snail is the same 
as that of the last locality, but when speaking of the Boulogne snail 
he calls it Helix aspersa. In this he is clearly mistaken. Perhaps 
some correspondent of the ‘ Zoologist’ may have the opportunity of 
examining the Tenby burrows, and telling us whether or not they 
are occupied by the “same species of Helix as that which forms the 
cavities in the limestone near Boulogne,” namely, H. hortensis. Mr. 
Hodgson speaks of the Whelpington burrower as Helix nemoralis, a 
title which, in the opinion of many conchologists, includes H. hor- 
tensis as a variety, and with this latitude the name may be employed 
by Mr. Hodgson. The name of the Sicilian snail is not given by 
M. Prévost. 
Mr. Jeffreys, in his recently published ‘British Conchology, 
ascribes to Helix aspersa the boring faculty, doubtless relying on 
the statement of Dr. Buckland. The evidence, however, of M. 
Bouchard-Chatereaux must be considered the more trustworthy. 
As bearing upon this subject, it may be mentioned that Mr. Jeffreys 
states that, according to M. Bonnafaux, the Helix aspersa has been 
known to perforate birds’ eggs in deserted nests, in order to feed on 
their contents. 
ALFRED MERLE NorRMAN. 
Sedgefield, February 20, 1864. 
On the External Parasites of Fish—May I ask the co-operation of the readers of 
the ‘ Zoologist’ in enabling us to arrive at a more accurate knowledge of the parasites 
which are to be found upon our marine and fresh-water fish? I am engaged in the 
iuvestigation ‘of both foreign and British species, and shall feel greatly obliged for any 
