CARDIUM. 



Trans, vol. viii. p. 64. — Dorset Catal. p. 31, pi. 4, f. 1. 



Wood, General Conch, p. 209, pi. 49, f. 3, 4. 

 Cardium parvum, Da Costa, British Conch, p. 177. 

 Encyclopedic Methodique, Vers, pi. 298, f. 1 . 



As the shape and parts of the present species most closely 

 resemble those of the succeeding, to avoid repetition, we 

 shall merely specify the particulars in which it differs. It 

 is a light, thin, bulky shell, and of far more ample dimen- 

 sions than the majority of the individuals of echinatum; its 

 tumidity, too, is not so evenly disposed, there being a mani- 

 fest, though not considerable, flattening of surface behind 

 the usual site of the umbonal ridge, causing a slight angu- 

 larity of curvature, preceding which is the chief convexity, 

 whilst the swell in the species we are comparing it with is 

 almost central. Its contour is far more angulated than in 

 the small ordinary suborbicular type of the latter, but very 

 nearly resembles the large variety of it which we have de- 

 lineated in our engraving. Its ventral margin, however, is 

 less arcuated ; its posterior lower angulation more decided, 

 its hinder edge rectilinear or subretuse (thus biangulating 

 the broad posterior extremity), and its anterior dorsal edge 

 is rather more sloping, which gives a marked projection to 

 the prominent umbones. The beaks seem less inclined for- 

 wards ; and the ligament is very large and elevated. The 

 surface has but little lustre, but is not utterly dull ; the 

 number of ribs ranges at least from eighteen to twenty-two, 

 which are often almost obsolete at the posterior extremity, 

 and not merely, as in echinatum, diminished in size and 

 elevation. They are rather less raised, too ; much flatten- 

 ed on their upper surfaces, and armed with rather large and 

 crowded spines ; of which the hinder rows (whose prickles 

 are generally the longest and largest) are sharp-pointed, 

 straight, and somewhat lancet-shaped, or laterally compress- 



