BIVALVIA. 53 
Mytinus Fuavus. Poli. Test. Sic., vol. ii, p. 207, pl. 32, fig. 4, 1795. 
— saGiTTaTus. Id. - - - 208, - figs. 2, 3. 
— UNGULATUS. Id. - - - 209, - fig. 5. 
= GALLOPROVINCIALIS. Desh. 2d ed. Lam., t. vii, p. 46. 
— ABBREVIATUS. Id. - - -  p. 47, No. 30. 
— RETUSUS. Td. - - Hens 4057 7 Ob. 
— BOREALIS. Dekay. Nat. Hist. New York Zool., p. 182, pl. 13, fig. 222. 
— pitaratus. MW. Wood. Ind. Test. Sup., pl. 2, Myviu., fig. 2. 
= SUBSAXATILIS. Williamson. Mag. Nat. Hist., 1834, vol. vii, p. 354, fig. 48, a—d 
— ANGULATUS. Alder. MSS., fide Williamson. 
— souitarius. Rev. W. Mark. MSS. Id. 
— notatus. Dekay. Nat. Hist. New York Zool., p. 182, pl. 13, fig. 223, 1843. 
— ANTIQUORUM. J. Sow. Min. Conch., t. 275, figs. 1-3, 1821. 
— — Desh. 2d ed. Lam., vii, p. 54, 1836. 
— Nyst. Rect. Coq. Foss. Prov. d’Any., p. 17, No. 66, 1835. 
— — Phil. En. Moll. Sic., vol. i, p. 73, and vol. ii, p. 53. 
= — Nyst. Coq. Foss. de Belg., p. 267, pl. 21, fig. 1, a—é. 
— — Basterot. Mem. Geol. des Envy. de Bord., p. 78, 1825. 
— —= Woodward. Geol. of Norf., p. 44, t. 2, fig. 20, 1833. 
— AL@ForMIs. J. Sow. Min. Conch., t. 275, fig. 4, 1821. 
— — Woodward. Geol. of Norf., p. 44, 1833. 
— AFFINIS. Bean. MSS. (not Sowerby). 
— PLEBEIUS? Dubois de Montp. Conch. Foss. de Wolhyn. Podol., p. 69, pl. 7; 
figs. 26-28, 1831. 
— EpuLIS. Brocchi. Conch. Foss. sub. Apen., p. 584, 1814. 
a — Bast. Mem. Geol. des Envy. de Bord., p. 79, 1825. 
Spec. Char. Testa elongato-trigonuld, levigatd ; anterius curvd, subangulatd ; posterius 
retusd ; versus basim tumidd ; dentibus tribus vel quaternis. 
Shell elongate, of a subtrigonal form, smooth, anterior part curved, subangulated, 
posterior obtuse, tumid towards the base, hinge with three or four denticles. 
Greatest diameter, 4 inches. 
Locality. Red Crag, Sutton, Bawdsey, Ipswich. 
Mam. Crag, Bramerton, Bridlington. 
Recent, Mediterranean, Britain, Scandinavia, and North America. 
The true edible species is first seen in the Red Crag Deposit, and is found in some 
places, as might be expected, in great abundance, but the specimens have become so 
thin and fragile, as to be with difficulty procured entire. 
What is considered as the normal form of this species, by Messrs. Forbes and 
Hanley, is that variety which has been erected into a distinct species by Mr. 
Williamson, under the name sw4savatilis. In this the shell is more angular, and the 
posterior portion becomes broader, its solitary habits giving free scope to an expansion 
at that part, and enabling it to assume what may be called its natural shape. This 
variety has not been met with by myself in the Red Crag, but it is by no means 
uncommon in the deposit at Chillesford which rests upon it, and which probably 
belongs to the mammaliferous or more recent period, and where it is the only 
