Mr. Jeflfreys on British Molluscn. 115 



the shell was brought to liim by our dredger, it had a good deal 

 of the epidermis adhering to it, of most of which, however, the 

 shell has been unfortunately deprived in an attempt to clean it. An 

 eminent naturalist, to whom the specimen was submitted for his 

 opinion, pronounced it to be recent, because of its retaining the 

 epidermis ; but the persistence of such substances seems to be co- 

 eval with shells which are undoubtedly fossil. In answer to an 

 inquiry I have made of Mr. Searles Wood on the subject, he says, 

 " There cannot be much difference of opinion respecting the preserva- 

 tion and existence of the epidermis and ligament in the fossils of the 

 uppermost Tertiaries in this country. I do not see the epidermis 

 upon the few specimens of Cyrena in my cabinet ; but in a specimen 

 of Unio liftoralis from Clacton I am now looking at, the valves are 

 united and the ligament quite perfect, and it has on it some of the 

 epidermis ; besides which, the ligament is preserved on some of the 

 Crag bivalves which are of older date." 



Lachesis minima, iii. 577 ; var. alba. Guernsey ; but rare. 



Litiopa Bombyx. In Mr. Pickering's fine collection of British 

 land and freshwater shells, I noticed a specimen appearing to be- 

 long to this pelagic species, and which he had taken at Gravesend, 

 mixed with Rissoa centrnsa and other unquestionably indigenous 

 shells. It is, however, much smaller than L. Bombyx, and has the 

 upper whorls minutely tuberculated, the rest of the shell being 

 smooth ; so that it may be a species of Melanopsis. If the former, 

 it has probably been dropped from Gulf-weed {Sargassum vulgare), 

 which is known occasionally to ^^sit our shores. Mr. Lukis told me 

 that he saw, about fifty years ago, in a small bay at Guernsey, a 

 bank of this weed, several feet high, which had been thrown up by 

 the sea. 



Triforis adversa. Cerithium adversum,m. \9d. A pale yellowish- 

 white variety occurs in Guernsey ; but it is very rare. The siphonal 

 fold of the mantle, and the peculiar canal of the shell, are surely 

 sufficient grounds for separating this genus from Cerithium, inde- 

 pendently of its being always heterostrophe. Some of these charac- 

 ters indicate a nearer relation to Cerithiopsis than to Cerithium. The 

 operculum is, however, Littorinan. 



Cerithiopsis tubercularis, iii. 365. Mr. Norman says that a 

 specimen in his cabinet, from Arran, N. B., measures 5 lines long 

 and I i broad, and that it has fourteen whorls remaining, at least 

 three more having been broken off". 



C. pulchella, var. alba. Guernsey. 



C. metula. Cerithium metula, iii. 198. My largest specimen, 

 which is from the Shetlauds, measures more than y'^^ths of an inch in 

 length and ^ths in breadth. Although the animal is not known, 

 the deep canal of the shell, as well as the operculum, which is strictly 

 Muricidal, would, I think, entitle it to a position in Cerithiopsis, and 

 not in Cerithium. 



C. Naiadis. One of the results of our Zetland dredgings was the 

 acquisition of two small and imperfect specimens of a new and inter- 

 esting species, which Mr. ^I 'Andrew took on the coast of Norway. 



8* 



