BIVALVIA. 215 



1. Artemis lentiformis, /. Soxverhj. Tab. XX, fig. 7 a — c. 



Venus exoleta. Parkinson. Org. Rem., vol. iii, p. 189, 1811. 



— LENTiFOEMis. J. Sow. Min. Conch., t. 203, 1818. 

 Aetemis exoleta. Nyst. Coq. Foss. Belg., p. 184, pi. xiv, fig. 1, 1844. 



— LENTIFOEMIS. S. Wood. Catalogue, 1840. 



— ,, — Potie: et Mich. Catal. des Moll, de Douai, torn, xi, p. 227, No. 13, 



1844. 



Sjjec. Char. Testa orbiculari, lentiformi, compressiusculd incequilaterali, crassd; striis 

 concentricis, magnis, confertis ; lunula cordatd, impressd; margine dorsali convexiusculo 

 postice subanguJafo. 



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

 covered with numerous large, close set, concentric strife ; 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 difi"er 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 o-reat 

 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 stride or rido-es are 

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

 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 striae or fine lines of o-rowth. 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, Pulteneg. Tab. XX, fig. 6 a — d. 



Venus lincta. Pult. Hutchins, Dorset, p. 34, fide Forb. and Hani. 



— EXOLETA. Peim. Brit. Zool., vol. iv, p. 94, pi. hi, 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. Pali. Test. Sicil., t. xxi, fig. 8. 



— LACTEA. Mont. Test. Brit. Sup., p. 4G, 1808. 



28 



