American Slipper-Limpet. 497 



present year the westward range was extended by the dis- 

 covery by Col. Worthington Wilmer of shells of the species 

 atRyde (Isle of Wight). 



Hitherto no records have been forthcoming of the extension 

 of the animal's range up the East Coast from the Oolne 

 estuary. However, in September of the present year I 

 received a number of shells of the species from Miss B. 

 Nicholson, who had found them on the beach at Frinton-on- 

 Sea (Essex). Miss Nicholson informs me that she found the 

 same form at Frinton in 1914, only in far less quantity than 

 in the present year. 



Having some knowledge of the features of the N. Essex 

 coastal waters, I thought it would be interesting to follow 

 Miss Nicholson's discovery up. I accordingly communicated 

 with persons at Walton-on-Naze,Dovercourt, and Woodbridge 

 Haven, and, as a result, found that Crepidula fornicata has 

 established itself all along the Essex and Suffolk coast from 

 Frinton to the mouth of the River Deben (Woodbridge 

 Haven). I hope that field-naturalists will follow up this 

 clue and attempt to determine its present range and record 

 its further progress. 



A few remarks upon the method by which this species is 

 extending its range may be offered at this point. In the 

 first place, it is highly probable that the extension up the Essex 

 coast from Mersea Island and the mouth of the Oolne River, 

 at least along the Clacton-Frinton coast-line, was effected by 

 the free-swimming larva. Orton has pointed out (3) that the 

 spat of Crepidula can be caught upon floating rafts; so it is 

 not impossible that the larvse might settle down upon the 

 submerged and projecting parts or tackle of a coasting vessel 

 plying between the places involved, just as they settled down on 

 the raft in the experiment described by Orton. But, owing to 

 the excessive shallowness of the water off Frinton, no coasting 

 vessels call there. It is just possible that yachts that lie up 

 at Brightlingsea during part of the year, and during the rest 

 are used off the coast, may have carried spat about with 

 them, but the number of such yachts that visit Frinton is 

 very small. With regard to the extension of range to Dover- 

 court and the Suffolk coast, it is possible that a small coaster 

 or sea-going wherry may have acted as the disseminating 

 agent, carrying the spat from the Colne estuary to Harwich 

 and Woodbridge Haven (the latter being accessible to 

 coasting traffic). Dovercourt, on the other hand, is not visited 

 by coasting traffic for the same reason as Frinton is not. On 

 the other hand, the animal may be effecting its extension of 

 range entirely in the larval (free-swimming) stage. In this 

 Ann. & Mag. N. Hist. Ser. S. Vol. xvi. 35 



