SEA-FISHERIES LABORATORY. 179 
are, as a rule, found only in sheltered waters, in shallow 
bays, and at the mouths of estuaries. There is great con- 
stancy in the characters of the cockles from the various 
parts of the Lancashire and Cheshire coasts, no well-marked 
varieties being found. The difference in size observed in 
specimens from various parts of this district are most 
probably due to the extent to which the beds have been 
fished or disturbed in late years. Generally the influence 
of some fresh water* seems to be favourable in that cockles 
are more abundant in the neighbourhood of the mouths of 
rivers, but the largest specimens are found only in areas 
far removed from the influence of fresh water. Large 
cockles, with shells two inches in length, are found on 
some parts of the North Coast of Devon, in Barra, in the 
Western Hebrides, and in the Scilly Isles. In Barra 
these large cockles are sufficiently numerous to form the 
material for an important fishery. Such giant forms are 
not found on the Lancashire coast, where the average 
length is about one and a half inches. Here the market- 
able cockle has a minimum breadth of $ inch, the size being 
fixed by the Sea-Fisheries Committee’s Bye-law. With 
the exercise of proper care on the part of fishermen to 
take only well-grown animals, there can be no doubt that 
the Lancashire and Cheshire cockle fisheries might be 
more largely developed, since the physical conditions are 
so suitable. 
The cockle inhabits the topmost layer of the sand, 
burying itself to the depth of an inch at most. It lies in an 
oblique position, and, when the bed is covered with water, 
with the siphons projecting slightly above the surface 
* The influence of extreme salinity or freshness, as might be expected, is to 
produce well-marked variations in the character of the shell. See Bateson, 
Phil. Trans. Roy. Soc., vol. CLXXX. B., pp. 297—330, 1889; and Forbes 
aud Hanley, History of the British Mollusca, 1850, vol. II., p. 21. 
