On the Structure and Life-PIistory of the Common 

 Cockle, with an Appendix on the Lancashire 

 Cockle Fisheries, with Pis. I. — VI. and Map. 



(J. Johnstone.) 



[Note : — This investigation into the structure of the 

 cockle was carried out mainly in the Fisheries Labora- 

 tory at University College, Liverpool ; but in part also 

 at the Sea-Fish Hatchery at Piel — which was found 

 most convenient for the study of living specimens. 

 Most of the material used was obtained from the cockle 

 beds in the Mersey estuary, and was collected and sent 

 to the Laboratory by Mr G. Eccles, cliief fishery 

 officer at New Brighton. Specimens were also sent 

 by Mr. Andrew Scott from the Baicliff beds and those 

 in the immediate neighbourhood of Piel. 1 



I 



The edible cockle {Cardium edule) is by far the commonest 

 member of the genus Cardium, a group of eulamelli- 

 branchiate Mollusca having a world-wide distribution and 

 containing a great number (about 200) of species. The 

 number of British species is, however, limited to ten, 

 most of which (C. ecJiinatum, C. fasciatum, C. edule, C. 

 mininmim, C. norvegicum, G. nodosum) are recorded as 

 being present in the Irish Sea; of these the only abundant 

 species is C. edule; C. norvegicum {Lcvvicardium) is fairly 

 common, the others being only occasionally found. The 

 different species seem to have a fairly well-marked bathy- 

 metrical range, but C. edule is found from between tide 

 marks out to 1360 fathoms. Here and over the greater 

 part of Europe C. edule is the only species of any economic 

 importance ; in Jersey, however, C. norvegicum is used for 

 food, and in the Mediterranean various other species are 

 eaten. 



The edible cockle is gregarious all along the coast line 

 where suitable bottoms exist, but the great cockling beds 



