160 MOLLUSCA FROM THE CRAG. 
almost to have obliterated the radiating ridges. There appear to have been periods in 
the life of the animal when the margin of the shell was more than ordinarily thickened, 
as if the process of increase in the shell was delayed or interrupted, after which it 
proceeded with more slender rays until they were again thickened, or rather strength- 
ened. This fossil strongly resembles a northern form found in the sea of Ochotsck, 
figured by Middendorff in his ‘ Russian Malacology,’ t. xv, figs. 23—25, described 
under the name of C. Californiense, Desh., but it is, I believe, specifically different, as in 
that species (according to the figure) the posterior side is much less rounded than in 
our Crag fossil; the hinge also appears thicker, with a wider fulcrum for the ligament. 
10. CARDIUM vENUSTUM, S. Wood. Tab. XIII, fig. 2 a—dé. 
Dale. Hist. and Antiq. of Harwich, p. 293, pl. xii, fig. 18, 1730. 
Spec. Char. Testa cordato-ovatd, obliqud, inequilaterali; obsolete costatd, costis nume- 
rosis depressis ; latere postico levigato. 
Shell ovately heartshaped, oblique, inequilateral ; obsoletely costated, ribs nume- 
rous, depressed ; posterior side smooth, naked. 
Length, 2 inches ; height, 2 inches. 
Localities. Red Crag, Walton-on-the-Naze, Sutton. 
This is one of the rarer shells of the Red Crag. Being unable satisfactorily to 
assign it to any known species, I am reluctantly obliged to give ita new name. The 
shell figured by Dale is evidently the same as ours, but I cannot, as he has done, refer 
it to Lister’s figure, which is C. Worvegicum; there is a strong general resemblance, but 
the posterior side is too much rounded to be united with that species, and it was 
probably a smoother shell than C. decorticatum of the Coralline Crag. 
11. CarpiuM GroENLANDIcuM, Chemnitz. Tab. XIII, fig. 1 a—d. 
Carpium GRoENLANDICUM. Chemn. Conch. Cab., t. vi, p. 202, t. xix, fig. 198, 1782. 
= = Gould. Invert. Massach., p. 92, 1841. 
— Moller. Ind. Moll. Groen., p. 20, 1842. 
— — Dekay. Nat. Hist. New York Zool., p. 206, pl. xxiii, fig. 250. 
— Reeve. Conch. Icon. Card., pl. x, fig. 53. 
— Middendorf’. Malacozoologia Rossica, (Mém. de l’Acad. Imp. 
des Sci. St. Petersb.,) p. 557, t. xvi, figs. 6—9, 1849. 
—  eEpEntuLA. Mont. Test. Brit. Suppl., p. 29, 1808. 
—  EDENTULUM. G. Sow. Genera No. 34, Cardium, fig. 2. 
—  anoponta. Blainv. Man. Malac., p. 658, 1825. 
—  BorEALE. Reeve. Conch. Icon., pl. xxii, fig. 131. 
MactTra RADIATA. Don. Brit. Shells, vol. v, t. 161, 1803. 
APHRODITA COLUMBA. J. Lea. Trans. Amer. Phil. Soc., vol. v, p. 110, pl. xvii, fig. 54, 1833. 
Acarpo. Swains. Treat. Malac., p. 374, 1840. 
Surrrpes. Beck. Fide Gould. 
Monopacna proprnqua? Hichwald. Fauna Caspio-Caucasia, p. 275, t. xl, figs. 3, 4, 1841. 
?Encye, Method., t. 300, fig. 7. 
