156 MOLLUSCA FROM THE CRAG. 



CABDIUM EDULINUM. Nyst. Ooq. Foss. de Belg., p. 193, pi. xv, fig. 1, 1843. 



ANGUSTANUM. Id. Eech. Coq. Foss. Prov. d'Anv., p. 13, No. 49, 1835. 



OBLIQ.UUM. Woodward. Geol. of Norf., p. 43, pi. ii, fig. 19, 1833. 



CLODIENSE. Broc. Coq. Foss. Subap., t. xiii, fig. 3, 1814. 



GLAUCUM. Brug. Encyc. Meth., t. i, p. 221, No. 14. 



LAMABCKII. Reeve. Conch. Icon. Cardium, pi. xviii, fig. 93. 



BELTICUM; Id. pi. xx, fig. 113. 



EICHWALDII. Id. pi. xix, fig. 94. 



Spec. Char. Testa variaMZe, plurimum rotundato-cordatd, obtiqud, interdum ovatd, 

 transversd, compressiusculd aut tumidd,parum incequilaterali costatd costis 18 28 postice 

 scepe obsoletis ; lineis concentricis elevatis, distantibus, asperis. 



Shell variable, for the most part roundedly heart-shaped, oblique, sometimes trans- 

 versely ovate, often tumid, occasionally compressed; ribs 18 28, the posterior obso- 

 lete ; concentrically rugose, with distant, dwarfish imbrications. 



Length, 2 inches ; heit/ht, \\. 



Localities. Cor. Crag, Ramsholt (var. rusticum). 

 Red Crag, passim. 



Mam. Crag, Bramerton, Thorpe, Chillesford. 

 Uddevalla. 



Recent, Mediterranean, Finmark, Britain, Caspian. 



The first indication of the existence of this species is in the Coralline Crag, from 

 which Formation I have only one specimen, and this is of the var. called rusticum / its 

 habits, however, in the living condition, are such as to confine it generally to shallow 

 water, and to the proximity of rivers, that its presence at Ramsholt in association 

 with species that are more purely marine, is not, perhaps, to be so much surprised at. 

 In the Red Crag, though not one of the most abundant, it is of common occurrence, 

 but the specimens are sometimes rubbed and worn, as if they had been much disturbed, 

 and probably transported from a distance : this is the state in which that variety 

 called edulinum by J. Sowerby, in ' Min. Conch.,' is most often found, and it is the one 

 most common there, and may, perhaps, have been derived from the older Formation, 

 or Coraline Crag. In the Red Crag the variations are very conspicuous ; in some the 

 diameter from the anterior to the posterior side greatly exceeds the measurement from 

 the umbo to the ventral margin ; in others it is slightly the reverse ; and the number 

 of ribs is alike variable ; the character most distinguishable is the slope on the pos- 

 terior side where the ribs are less prominent than upon the other parts of the shell, 

 but this is at times very indistinct, more particularly in that variety called clodiense 

 (fig. 2 e), which I believe to be only an aberrant form of this species. 



