BIVALVIA. 287 
of an individual measuring 1} inch long, and 2ths of an inch high, which was thought 
to be distinct from rugosa, and called striata. 1 cannot coincide in that opinion; it 
appears to me to be only a monstrous form of our variable shell. 
2. Saxicava arctica, Linneus. Tab. XXIX, fig. 4, a—d. 
Mya arctica. Linn. Syst. Nat., ed. 12, p. 1113. 
CaARDITA LITHOPHAGELLA. Costa. Fide Phil. 
Mya ELoneata. Broce. Coq. Foss. Subap., p. 529, t. 12, fig. 14, a, 6, 1814. 
HraTeLua arctica. Daud. Rec. Mem. Moll., 1800. 
ANATINA aRcTica. Turt. Brit. Biv., p. 49, pl. 4, figs. 7, 8, 1822. 
Saxicava arotica. Phil. En. Moll. Sic., vol. i, p- 20, t. 3, fig. 3, 1836. 
_— — Lovén. Ind. Moll. Scand., p. 40, 1846. 
— — D’ Orbigny. Moll. Canar., p. 109, No. 195, 1835. 
—_— — Nyst. Hist. Coq. Foss. Belg., p. 95, pl. 3, fig. 15, a—e, 1844. 
— rupra. Desh. Expéd. Algér. Moll., pl. 66, figs. 18, 19. 
SaXICAVA RHOMBOIDES. Desh. 2d ed. Lamarck, tom. vi, p-. 153, 1835. 
SoLen minutus. Linn. Syst. Nat., ed. 12, p. 1115, No. 42. 
— _— Mont. Test. Brit., p. 53, pl. 1, fig. 4, 1813. 
— puRPuREUS. Flem. Brit. An., p. 459, 1828. 
Hraretta Minura. Turt. Brit. Biv., p. 24, pl. 2, fig. 12, 1822. 
_ —_ Gray. List. Brit. Moll., p. 89, 1851. 
TELLINA RHOMBOIDES. Poli. Test. Sicil., p. 81, t. 15, figs. 12, 13, 15 ; and t. 14, fig. 16, 
Donax 1rvs. Olivi. Fide Philippi. 
Mytitus precisus. Mont. Test. Brit., p- 165, t. 4, fig. 2, 1803. 
PHOLEOBIA PR&CISA. Brown. Illust. Brit. Conch., t. 9, fig. 16. 
AGINA PURPUREA. Turt. Brit. Biv., p. 54, t. 4, fig. 9. 
DIDONTA BICARINATA. Schum. Essai, p. 125, pl. 6, fig. 2, a,.6, 1817. 
BraPHouius spinosus. ‘‘ Leach.” Ann. Mag. Nat. Hist., vol. xx, p. 272. 
Hypoe#a GIBBa. Poli. Test. Sic., vol. i, p. 251. 
Spec. Char. Testa crassd, oblongd, vel rhomboidali, valde inequilaterali ; concentrice 
striatd, aut rugosd ; latere antico brevissimo ; biseriatim obliqué aculeis instructo: cardine 
unidentato. 
Shell thick, oblong or rhomboidal, very inequilateral; rugose or irregularly 
striated with lines of growth; anterior side very short; ornamented with two 
diverging imbricated ridges: hinge with one tooth. 
Length, 3 inch. Height, 2 inch. 
Locality. Cor. Crag, Sutton. 
Red Crag, Sutton. 
Recent, Canary Islands, Mediterranean, A\gean, British and Norwegian Seas. 
In deference to the malacologists, I have separated these two shells, and placed 
them as distinct species, under the names arctica and rugosa, though I believe there is 
no ground for the distinction. 
