BIVALVIA. 163 



Chama GKrPHiNA. Lam. Hist, des An. s. Vert., t. vi, p. 97. 



— — Goldf. Pet. Germ., vol. ii, p. 205, t. 138, fig. 9 a—c. 



— — Phil. En. Moll. Sic, vol. i, p. 68, vol. ii, p. 49. 



— — Reeve, Conch. Icon. Chama, pi. viii, fig. 43. 



— SINISTRORSA. Chemn. Conch. Cab., vol. ix, p. 145, t. 116, figs. 992-3, 1786. 



— — Broc. Conch. Foss. Subap., p. 519, No. 3, 1814. 



— BicoRNis. Linn. Syst. Nat., ed. 12, p. 1139, No. 166, 1767. 



— UNICORNIS. Besh. 2d ed. Lamarck., t. vi, p. 582, 1835. 

 _ _ Phil. En. Moll. Sic, vol. i, p. 68, 1836. 



— UNICORNARIA. Lam. Hist, des An. s. Vert., t. vi, p. 98, 1815. 



— coRNUTA. Chemn. Couch. Cab., t. vii, p. 150, tab. lii, figs. 519-20. 



— LACERNATA. Desk. 2d ed. Lam., t. vi, p. 588, 1835. 



Spec. Char. Testa crasssd, irrec/ulariter orhiculari, imbricatd, lamellis brevibus, ap- 

 pressis ; apice valvulce inferioris si/iisfro?'sum incurvo. 



Shell thick, strong, irregularly orbicular, covered with short, close imbrications, 

 or lamellse ; apex of the lower or adherent valve curving to the left. 



Diameter. 2 inches. 



Localities. Cor. Crag, Sutton. 



Red Crag, Sutton and Newbourn. 



Recent, Mediterranean. 



This shell, in my cabinet, is very rare from the Coralline Crag, at the period of which 

 deposit it was an undoubted inhabitant of our latitude ; a few specimens have been 

 found in the disturbed portion of the Red Crag, but the solidity of the shell would 

 protect it in its possible removal from an older formation. In the few specimens 

 that I possess from the Red Crag, a somewhat greater difference appears to exist 

 between the two valves than is generally observable in C. gryphoides, or recent 

 variety, but that is so variable a character in the living shell as to give no warrant 

 for specific difference, depending, as it does, upon its mode of growth, or place of 

 attachment. 



The differences observable in C. grypldna and gryphoides appear to depend entirely 

 upon the mode by which the animal chooses to attach itself, the one by the right valve, 

 while the other is fixed by the left. In some species, as shown by Mr. Broderip, 

 (in the ' Trans, of the Zool. Soc.,') this mode of adherence is wholly eclectic, depending 

 upon the will of the animal, and that it almost as often employs the one valve as the 

 other for that purpose. 



In the var. grypldna the lower and larger valve, or that which has been the fixed 

 one, is the right, with the umbo taking a spiral or involute direction towards the left 

 hand, and the free valve appears more as an operculum to cover the animal, which 

 principally occupies the lower valve, like the oyster. In C. gryphoides this is reversed, 

 the left valve being made the adhering one, has consequently become the larger. Such 

 a character is a less organic change than we find exhibited in the two opposite forms 

 of Trophon antiquum, the spire of which, in the recent shell, . turns commonly to the 



