arcidjE. 137 



and does not seem to have undergone the least decom- 

 position; and the shell still retains its original colour 

 and gloss. The species has not been noticed by any 

 other writer, nor have I detected anything approaching 

 it in the extensive collections made by Dr. Torell on 

 the coasts of Iceland, North Greenland, and Spitzbergen. 

 There is some doubt as to the kind of bird from whose 

 crop the shells were extracted. Mr. Bean asserts that 

 that it was a Sanderling. Mr. Roberts is equally posi- 

 tive that it was a Brent-goose ; and he supports his state- 

 ment by the following domestic anecdote. Having 

 heard that a Brent-goose was excellent eating, he de- 

 pended on this bird for his Sunday dinner; but, to 

 his disgust, when his wife was preparing it for the spit, 

 it smelt so very " loud," that bread and cheese had to 

 be substituted. He attributed the smell to the decay- 

 ing Ulva on which the bird had fed, and among which 

 were the shells he had given Mr. Bean. Mr. Roberts 

 therefore had good reason for remembering what bird it 

 was that caused so much pleasure to Mr. Bean, but disap- 

 pointment to himself. Several specimens of this sin- 

 gular bivalve were taken on the above occasion. It 

 is figured in Sowerby's Illustrated Index to British 

 Shells, pi. 7.1 11. 



Family VI. AR'CID^, Lowe. 



Body thick, corresponding in shape with the shell : mantle 

 open in front, but in some genera forming a single fold or two 

 tubes at the posterior end : gills two on each side, arranged in 

 pairs : foot shaped like a disk, worm, axe, or tongue, capable 

 of burrowing, creeping, or spinning a byssus. 



Shell triangular, oval, wedge-shaped, round, oblong, or 

 rhomboidal, equivalve, inequilateral : epidermis thick : liga- 

 ment external ; certain genera have an internal cartilage in 



