194 MOLLUSCA FROM THE CRAG. 
Cuama cor. Poli. Test. Sic., vol. ii, p. 113, t. xxiii, fig. 1—3, 1795. 
— — Broce. Conch. Foss. Subap., p. 519, No. 4, 1814. 
Carpita cor. Brug. Encye. Meth. Vers., tom. i, p. 403, No. 1, 1792. 
— — Bosc. Hist. Nat. des Vers., t. ili, p. 85, pl. xxi, fig. 4. 
Isocarpia cor. Lam. Hist. des An. s. Vert., t. vi, p. 31, 1822. 
— — J. Sow. Min. Conch. t. 516, fig. 2, 1826. 
— — Goldf. Pet. Germ., vol. ii, p. 211, pl. 141, fig. 2a—e. 
— —  Bronn. Leth. Geogn., p. 941, pl. xxxvii, fig. 10, 1838. 
— — Phil. En. Moll. Sic., vol. i, p. 56, and vol. ii, p. 41. 
— — WNyst. Coq. Foss. de Belg., p. 196, pl. xvi, fig. 1 a, 6, e, 1844. 
_— —  Sysmonda. Syn. Meth. An. Inv. Pied. Foss., p. 18, 1847. 
—_ — Lovén. Ind. Moll. Scand., p. 36, 1846. 
—  GLopuLosa. Defrance. Dict. des Sc. Nat., t. xxiv, p. 180, Atlas, figs. 2, 2a. 
— Hresernica. Reeve. Conch. Icon. Isocard., pl. i, fig. 4. 
— VENTRICOSA. J. Sowerby. Min. Conch., vol. vi, p. 28. 
—  tvnunatTa. Nyst. Rech. Coq. Foss. Prov. d’Anv., p. 13, pl. iii, fig. 53, 1835. 
— — Id. Coq. Foss. de Belg., p. 189, pl. xv, fig. 2a—e, 1844. 
— CRASSA. Id. z= 7 p- 198, pl. xv, fig. 3a—e, 1844. 
— rustica. Conrad. Amer. Mioc. Foss., p. 20, pl. xi, fig. 1, 1838. 
—  PRATERNA. Say. Journ. Acad. Nat. Sci., vol. iv, p. 143, pl. xi, fig. 1a, b. 
— Marxort. Conrad. Proc. Nat. Inst., vol. i, p. 193, pl. ii, fig. 1. 
— Id. Amer. Mioe. Foss., p. 70, pl. xl, fig. 2, 1845. 
Giossts cor. Gray. List. Brit. Moll., p. 95, 1851. 
Spec. Char. Testd cordato-globosd, orbiculari, tumida, levigatd, valde inequilaterali ; 
umbonibus erassis, acutis, involutis et infra subexcavatis ; margine ventrali integro, acuto ; 
striis incrementt irregularibus, cardine bidentato. 
Shell somewhat orbicular, or globosely heartshaped, tumid, smooth, and very 
inequilateral ; umbones sharp, thick, and involute, beneath which the shell is depressed 
or subexcavated; ventral margin smooth and sharp, lines of increase irregular; hinge 
with two cardinal teeth in each valve. 
Diameter, 2 inches. 
Localities. Cor. Crag, Gedgrave, Ramsholt, Sutton. 
Red Crag, Sutton. 
Recent, Mediterranean, Britain, Sweden. 
This species is by no means abundant even in fragments, either in the Coralline or 
Red Crag. The specimen figured is from Gedgrave, and seems to resemble the variety 
now found in the Mediterranean, being smaller and more globose, with the umbones 
obtuse and very prominent, while the fragments from the Red Crag, as far as they can 
be determined, seem to approach the form of the variety found in our own seas, in 
which the shell is broader, with the umbones much depressed; this character consti- 
tutes the essential difference; the more tumid variety of the Coralline Crag corresponding 
with the Mediterranean form, as the conditions under which each existed were probably 
similar, while the Red Crag shell seems more to have resembled the one now living in 
the British seas. Our Crag specimens may be said to be smooth, with the exception 
of the irregular lines of growth; the numerous fine radiating strie which ornament 
