BIVALVIA. 215 



1. ARTEMIS LENTIFORMIS, /. Sowerby. Tab. XX, fig. 7 a c. 



VENUS EXOLETA. Parkinson. Org. Rem., vol. iii, p. 189, 1811. 



LENTIFOEMIS. J. Sow. Min. Conch., t. 203, 1818. 

 ARTEMIS EXOLETA. Nyst. Coq. Foss. Belg., p. 184, pi. xiv, fig. 1, 1844. 

 LENTIFORMIS. <S. Wood. Catalogue, 1840. 



Potiez et Mich. Catal. des Moll, de Douai, torn, xi, p. 227, No. 13, 

 1844. 



Spec. Char. Testa orbiculari, lentiformi, compressiusculd inaequilaterali, crassd ; striis 

 concentricis, magnis, confertis ; lunuld cordatd, impressd; maroine dorsali convexiusculo 

 postice subangulato. 



Shell orbicular, lentiform, somewhat compressed, slightly inequilateral, thick ; 

 covered with numerous large, close set, concentric striae ; a deeply-seated heartshaped 

 lunule ; dorsal margin slightly convex ; posterior side subangulated. 



Diameter, 2 inches. 



Localities. Cor. Crag? Gedgrave. 



Red Crag, Sutton, Walton-on-the-Naze. 



In the Coralline Crag it is very rare ; indeed I have obtained only one specimen, 

 which is represented at fig. 7 c, and this is partly imbedded in the matrix with its best 

 characters obscured ; but in the Red Crag it is one of the most abundant shells at 

 Walton-on-the-Naze. 



In the ' Mineral Concology' the Crag shell was considered to differ from Venus 

 exoleta (with which it had been placed by Parkinson) sufficiently to justify a specific 

 distinction, and as this is a genus in which the species do not appear to possess a great 

 range in variation, I have retained for it Mr. Sowerby's name, although these dif- 

 ferences are probably the effect of locality, or the result of external conditions. 



Our shell is certainly flatter than V. exoleta, but not thinner ; the striae or ridges are 

 as large and broad as those which ornament the recent species; there is a slight 

 angularity in the outline on the posterior side, a little beyond the termination of the 

 large ligament, and a slight slope upon the dorsal edge, differing therein from V. exoleta ; 

 this slope is not naked, but covered with numerous stria? or fine lines of growth. The 

 sinus in the mantlemark is large, deep, and linguiform in a direction across the shell ; 

 I have never seen a specimen with this sinus so vertical as it is represented in ' Min. 

 Conch.' above referred to. 



2. ARTEMIS LINCTA, Pulteney. Tab. XX, fig. 6 a d. 



VENUS LINCTA. Pult. Hutchins, Dorset, p. 34, fide Forb. and Hani. 



EXOLETA. Penn. Brit. Zool., vol. iv, p. 94, pi. Ivi, fig. 49. 



var. /3. Mat. and Rack. Linn. Trans., vol. viii, p. 87, pi. iii, fig. 2, 1807. 



SINUATA. Turt. Ed. Linn., vol. iv, p. 233, 1806. 



LUPINA. Poli. Test. Sicil., t. xxi, fig. 8. 



LACTEA. Mont. Test. Brit. Sup., p. 46, 1808. 



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