BIVALVIA. 287 



of an individual measuring 1 J inch long, and fths of an inch high, which was thought 

 to be distinct from rugosa, and called striata. I cannot coincide in that opinion ; it 

 appears to me to be only a monstrous form of our variable shell. 



2. SAXICAVA ARCTICA, Linnaeus. Tab. XXIX, fig. 4, a b. 



MYA ARCTICA. Linn. Syst. Nat., ed. 12, p. 1113. 



CARDITA LITHOPHAGELLA. Costa. Fide Phil. 



MYA ELONGATA. Broc. Coq. Foss. Subap., p. 529, t. 12, fig. 14, a, b, 1814. 



HIATELLA ARCTICA. Daud. Rec. Mem. Moll., 1800. 



ANATINA ARCTICA. Turt. Brit. Biv., p. 49, pi. 4, figs. 7, 8, 1822. 



SAXICAVA ARCTICA. Phil. En. Moll. Sic., vol. i, p. 20, t. 3, fig. 3, 1836. 



Lovtn. Ind. Moll. Scand., p. 40, 1846. 



D'Orligny. Moll. Canar., p. 109, No. 195, 1835. 



Nyst. Hist. Coq. Foss. Belg., p. 95, pi. 3, fig. 15, a -c, 1844. 

 RTJBRA. Desk. Exped. Alger. Moll., pi. 66, figs. 18, 19. 

 SAXICAVA RHOMBOIDES. Desh. 2d ed. Lamarck, torn, vi, p. 153, 1835. 

 SOLEN MiNUTUs. Linn. Syst. Nat., ed. 12, p. 1115, No. 42. 



Mont. Test. Brit., p. 53, pi. 1, fig. 4, 1813. 

 PURPUREUS. Flem. Brit. An., p. 459, 1828. 

 HIATELLA MINUTA. Turt. Brit. Biv., p. 24, pi. 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 IRUS. Olivi. Fide Philippi. 



MYTILUS PR^CISUS. Mont. Test. Brit., p. 165, t. 4, fig. 2, 1803. 

 PHOLEOBIA PR^ECISA. Brown. Illust. Brit. Conch., t. 9, fig. 16. 

 AGINA PDRPUREA. Turt. Brit. Biv., p. 54, t. 4, fig. 9. 

 DIDONTA BICARINATA. Schum. Eesai, p. 125, pi. 6, fig. 2, a, b, 1817. 

 BIAPHOLIUS SPINOSUS. " Leack." Ann. Mag. Nat. Hist., vol. xx, p. 272. 

 HYPOG^A GIBB A. Poli. Test. Sic., vol. i, p. 25 1 . 



Spec. Char. Testa crassd, oUongd, vel rhomboidali, valde inaquilaterali ; concentrice 

 striata, aut rugosd ; latere antico brevissimo ; biseriatim oblique aculeis instructo: car dine 

 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, f inch. Height, f inch. 



Locality. Cor. Crag, Sutton. 

 Red Crag, Sutton. 

 Recent, Canary Islands, Mediterranean, ^Egean, 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. 



