BIVALVIA. 217 
GASTRANA,* Schum. 1817. 
Trritna (sp.) Linn. Chemn. 
Venus (sp.) Retz. 1788. 
PsamMosia (sp.) Lam. 1818. Turt. 1822. Flem. 1828. 
Perricoua (sp.) J. Sow. Lam. 
Dioponta. Desh. 1845. orb. and Hanl. 1848. Gray, 1851. Woodward, 1854. 
Generic Character. Shell equivalved, inequilateral, transverse, ovate or subtrigonal, 
covered with concentric striz or lamellae. Hinge with two teeth in one valve, and 
one large subbifid tooth in the other. Impressions by the adductors ovate, nearly 
equal, that by the mantle with a sinus wide and deep. Ligament external. 
Animal with the mantle open, and fimbriated margins; siphons long, unequal, and 
separated to their bases, with slightly fringed orifices ; foot linguiform. 
This appears to be a very well marked genus, and strongly characterised by its 
dentition. A few species only are as yet known either in a recent or fossil state. 
I have not seen it from any older formation than the Faluns of Touraine. One 
fossil species has been brought from South Africa, belonging to a tertiary deposit. 
1. GASTRANA LAMINOSA, J. Sowerby. Tab. XXV, fig. 1, a—e. 
PETRICOLA LAMINOSA. J. Sow. Min. Conch., t. 573, 1827. 
— _— Nyst. Coq. Foss. de Belg., p. 99, pl. 3, fig. 16, 1844. 
Spec. Char. Testa subirregulari, ovatd vel trigonuld, conveviusculd, clausd, inequi- 
laterali ; antice rotundatd, postice angulatd ; lamellatd, lamellis erectis acutis, striis 
interstitiis exilioribus ; cardine bidentato ; sinu palliari magno. 
Shell somewhat irregular, slightly convex, ovate or trigonular, closed, inequilateral ; 
anterior side rounded, posterior angulated; covered with sharp and erect concentric 
ridges or lamellx, and very fine radiating striz between them; hinge with two teeth, 
palleal sinus large. 
Length, 2% inches. Height, 13 inch. 
Locality. Cor. Crag, Ramsholt, Gedgrave, Sutton. 
Red Crag, Sutton, Alderton, Bawdsey, Walton Naze. 
This species is not particularly rare either in the Coralline or in the Red Crag. 
It has considerable resemblance to Tellina fragilis, Linn. (Petricola ochroleuca, Lam.), 
but appears to differ sufficiently to be removed from that species. Like it, however, it 
was subject to much distortion; and though the valves are found free, its habits were 
probably such as to lead it into confined situations, so as oftentimes to impede the 
* Etym.? yaoryp, ventral. 
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