[437 ] 



An Account of the Natural History of the 

 Slipper-Limpet 



{Crepidu/a fornicata), 



With some remarks on its occurrence on the Oyster Grounds on 



the Essex Coast.* 



By 

 J. H. Orton, B.Sc. 



The American limpet, or slipper-limpet, known to naturalists as 

 Crcpiclida fornicata, was introduced into England about 1880, being 

 recorded at that time by Mr. B. S. Dodd in the Proceedings of the 

 Malacological Society for 1893. Dodd, it is interesting to note, 

 sounded even at that early time a warning note against the possible 

 spread of this animal, and the probability of its becoming an enemy 

 to the oyster farmer. There is no doubt that this limpet has been, 

 and is probably still being introduced along with American oysters, 

 on which it fixes itself. I have myself seen it unshipped along with 

 oysters, but all the specimens I found had died recently. The spread 

 of the limpet appears to have been very rapid on some grounds, as, 

 for example, at West Mersea, where, since its appearance about eight 

 years ago (from information obtained from local oyster fishermen), 

 it has spread so that it is now more common than oysters. 



The rapid spread of Crepidula on this coast is probably due chiefly 

 to the abundance of the kind of food which the animal likes, and I am 

 able to show that Crepidula feeds on exactly the same food as 

 oysters. Thus the suitability of the Essex coast for the culture of 

 oysters rendered it equally suitable for the spread of Crepidula. The 

 mode of feeding of Crepidula is the same in principle as that of 

 the oyster. Water is drawn in and expelled at the front end of the 

 shell; the ingoing current entering on the left side, passing over the 

 back of the animal, and out at the right side, as indicated in the 

 accompanying diagrams (seef page 447, Figs. 1 and 2). Between the in- 

 going and outgoing currents the gill of the animal acts as a strainer, 

 which collects all the food material that occurs floating in the 



* Printed by the Kent and Essex Sea Fisheries Committee, January, 1912, for distribution 

 amongst the Committee. 



t These figures are incorporated in another and fuller account of the mode of feeding 

 of Crepidula (see pp. 444-78 of tliis number) which was written subsequently to the 

 printing of this Report. 



