BIVALVIA. 207 
of Venus, which has the outer portion of a fibrous character, while in this it is more 
compact, and in the recent shell is often enamelled. 
This genus is found extensively in the warmer regions of the globe; as a fossil it 
has been obtained very low in the secondary Formations, and was largely developed 
during the early Tertiary Periods. 
1. CyTHEREA CHIONE, Linnaeus. Tab. XX, fig. 4a, 6. 
Cuama. Regenfuss. Choix Coquil., p. 56, t. viii, fig. 17. 
Curvirostrum. Leigh. Nat. Hist. Chesh., p. 179, pl. iui, fig. 5, 1700. 
Venus cutone. Linn. Syst. Nat., ed. 12, p. 1131, No. 125, 1767. 
— _ Poli. Test. Sicil., vol. ii, p. 85, pl. xx, figs. 1, 2, 1795. 
_— — Broce. Conch. Foss. Subap., p. 547, 1814. 
— — Sismonda. Syn. Meth. Invert. Foss. Ped., p. 19, 1847. 
— cutonom:s? Nyst. Coq. Foss. de Belg., p. 175, pl. xii, fig. 5 a, 6, 1844. 
PECTUNCULUS GLABER. Dacosta. Brit. Conch., p. 184, pl. xiv, fig. 7, 1778. 
Drone GLABER. Gray. List Brit. Moll., p. 6, 1851. 
Cyruerna cutone. Turt. Brit. Biv., p. 160, pl. viii, fig. 11, 1822. 
— — Payr. Catal. Moll. Corse., p. 47, 1826. 
—_ — Bronn. Leth. Geogn., ii, p. 994, t. XXxViii, fig. 3a—e, 1838. 
—_ —— Phil. En. Moll. Sic., vol. i, p. 40, vol. u, p. 31. 
— _— Owen. Comp. Anat. Invert. An. p. 282, fig. 118, 1843. 
— — Forbes. gean Invert. Rep. Brit. Assoc., p. 180, 1843. 
a — Agass. Icon. des. Coq. Tert., p. 45, t. x, figs. 10—13, 1845. 
— wirens. Andr. Bull. de Sc. de Mose. p. 104, pl. vi, fig. 9, 1830, fide Bronn. 
— .L#®vis. dgass. Loc. cit. supra, t. x. 
CyTHERKE Fauve. Chenu. Traité Element., pl. iii, fig. 10. 
Encyc. Method., pl. 266, fig. 1 a. 4, 
Spec. Char. Testdé transversd, ovato-cordatd, inequilaterali, glabra, politd, trans- 
versim obsolete sulcatd ; lunuld elongata ; antice et posticé rotundata. 
Shell transverse, ovate, heartshaped, inequilateral, very smooth, and glossy ; with 
obsolete transverse ridges; lunule elongate, and cordiform: anterior and posterior 
sides rounded. 
Length, 24 inches; height, 1} ditto. 
Locality. Cor. Crag, Ramsholt 
Recent, Britain, Mediterranean. 
This elegant and beautiful shell I have seen only from the oldest of the Crag 
Deposits, and in that from the lowest part, where it is not rare, but of extreme 
fragility, and specimens are very difficult to be obtained. 
The Crag shell agrees precisely with the British form of this species, in the exterior 
being smooth and glossy, and marked in a concentric direction, with occasionally 
shallow or indistinct furrows, or depressions, and with the aid of a lens may be seen 
numerous, fine, radiating striae, most visible upon the posterior side; these, however, 
are quite superficial, and are not seen when the surface is removed, nor is it imparted 
in any way to the margin of the shell which is quite smooth. 
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