194 MOLLUSCA. FROM THE CRAG. 



Chama cor. PoH. Test. Sic, vol. ii, p. 113, t. xxiii, fig. 1 — 3, 1795. 



_ _ Brof. Conch. Foss. Subap., p. :. 19, No. 1, 181-1. 

 Cardita coe. Jiruff. Encyc. Mcth. Vers., torn, i, p. 403, No. 1, l"t)2, 



— — Bosc. Hist. Nat. des Vers., t. iii, p. 8;"), pi. xxi, fig. -1. 

 Isocardia cor. Lam. Hist, des An. s. Vert., t. vi, p. 31, 1822. 



— — J. Sow. Min. Conch, t. 51 G, fig. 2, 1826. 



— — Gold/. Pet. Germ., vol. ii, p. 21 1, pi. 141, fig. 2 a—c. 



— — Bronn. Leth. Geogn., p. 941, pi. xxxviii, fig. 10, 1838. 



— — Phil. Eu. Moll. Sic., vol. i, p. 56, and vol. ii, p. 41. 



— — Nijst. Coq. Foss. de Belg., p. 196, pi. xvi, fig. 1 a, h, e, 1844. 



— — Si/smonda. Syu. Meth. An. Inv. Pied. Foss., p. IS, 1847. 



— — Loven. Ind. Moll. Scaud., p. 36, 1846. 



— GLOBCLOSA. De/rance. Diet, des Sc. Nat., t. xxiv, p. 180, Atlas, figs. 2, 2 a. 



— HiBERXicA. Reeve. Conch. Icon. Isocard., pi. i, fig. 4. 



— VEXTRicosA. J. Sowerby. Min. Conch., vol. vi, p. 28. 



— LUNCLATA. Ntjst. Kcch. Coq. Foss. Prov. d'.Vnv., p. 13, pi. iii, fig. 53, 1835. 



— — /(/. Coq. Foss. de Belg., p. 189, pi. xv, fig. 2a— e, 1844. 



— CKASSA. Id. „ „ p. 198, pi. XV, fig. 3 a — e, 1844. 



— EUSTICA. Conrad. Amer. Mioc. Foss., p. 20, pi. xi, fig. 1, 1838. 



— FRATEKNA. i<aij. Journ. Acad. Nat. Sci., vol. iv, p. 143, pi. xi, fig. 1 a, h. 



— Maekoei. Conrad. Proc. Nat. Inst., vol. i, p. 193, pi. ii, fig. I. 



— — Id. Amer. Mioc. Foss., p. 70, pi. xl, fig. 2, 1845. 

 Glosscs cor. Grai/. List. Brit. Moll., p. 95, 1851. 



Spec. Char. Testa cordato-glohosd, orbiculari, tumidu, lavigatd, valde inesquilaterali ; 

 umbonibus crassis, actttis, involutis el infra subewcavatis ; margine ventraliintegro, acuta ; 

 striis incrementi irregularibus, cardine bidentato. 



Shell somewhat orbicular, or globosely heartshaped, tumid, smooth, and very 

 incquilatcriil ; umboncs shaq), 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 bv no means abundant even in fragments, cither 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 nmch 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 e.\isted 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 strias which ornament 



