DEXTALIITM. 197 



Red and Coralline Crag (S.Wood). It has nine lon- 

 gitudinal ribs, besides frequently a stria between each 

 rib, but no fine impressed lines as in D. Tarentinum ; and 

 it is more angulated. This may have been the shell 

 of which Miss Pocock found several specimens " on the 

 sandy coast of Cornwall, near Lelant, in the year 1802/' 

 but which Donovan mistook for another species and 

 named D. octangulatum. Perhaps D. dent alls may 

 hereafter be discovered on our southern or Irish coasts. 

 It is the D. novemcostatum of Lamarck, and D. vulgare 

 of H. and A. Adams. 



D. abyssorum of Sars once lived, and possibly sur- 

 vives, in our northern seas, I dredged two or three 

 young specimens in Shetland on different occasions; 

 but they had a semifossilized look. This species in- 

 habits the western coasts of Sweden and Norway, at 

 depths varying from 40 to 150 f. Sars has identified it 

 with D. striolatum of Stimpson from the east coast of 

 North America ; and it is most likely the D. attenuatum 

 of Say from Massachusetts. D. abyssorum is one of 

 our glacial relics ; it occurs in the boulder- clay at Brid- 

 lington (S. Wood, as " D. entale") and Wick (Peach) ; 

 Moel Tryfaen (Darbishire) ; Banff (Forbes, as D. den- 

 talis); Preston (J. Smith, as D. striatum); newer and 

 older deposits at Chris tiania (Sars), in the former 

 at 100-120 feet, and in the latter at 460 feet above the 

 sea-level. It is longer and thinner than D. dent alia, 

 and has more ribs : it is not so finely striated as D. 

 Tarentinum, and wants the impressed lines. The ter- 

 minal process is like that of D. entails. 



D. striatum of Born (D. octangulatum, Donovan, D. 

 octogonum, Lamarck, and D. striatulum, Turton) is a 

 tropical shell, and has been wrongly considered British 

 on very suspicious authority. Turton' s collection con- 



