BIVALVIA. 157 
6. CARDIUM ANGUSTATUM, J. Sowerby. Tab. XIII, fig. 6 a—e. 
CarDIUM ANGUsTATUM. J. Sow. Min. Conch. t. 283, fig. 2, 1821. 
_ _ Woodward. Syn. Tab., p. 13, 1830. 
_ _ S. Wood. Catalogue, 1840. 
Spec. Char, Testd transversd, elongato-ovatd, parim inequilaterali ; depressiusculd, 
tenui ; anticé rotundatd, inflata; postice attenuata, compressiusculd; costis 27—82 depressis, 
planulatis, approximatis, asperis ; margine ventrali recto vel coarctato. 
Shell transverse, elongato-ovate, slightly inequilateral, somewhat depressed, 
thin; anterior side rounded, and inflated, posterior attenuated, and compressed ; 
ribs 27—32, depressed, flattened, approximating, roughened; ventral margin 
straight, or rather contracted. 
Length, 1} inch; height, 1 inch. 
Localities. Red Crag, Sutton, Bawdsey, Ramsholt, Alderton. 
This species is very abundant in one or two localities, and it does not appear to 
have been as yet met with in any other part of the World than in the Red Crag. 
In ‘Min. Conch.’ above referred to, vol. iii, p. 149, it is stated to be abundant in 
the Crag of Norfolk, but it is not enumerated amongst the shells from near Norwich by 
Woodward, nor have I seen a specimen from that Formation. This species may be well 
determined, although occasionally it presents some difference in outward form, but the 
posterior side is always more or less attenuated, and the dorsal margin on that side 
slopes at a considerable angle from the umbo; the line of the ventral margin, also, in 
that half of the shell, is contracted or drawn inwards, giving it a pointed form, 
considerably more so than in any variety of the common cockle, from which it also 
differs in having a greater number of ribs, and these are flatter. The umbo is nearly 
equidistant from each extremity, but the posterior side is much the smaller; the marks 
of the ribs are very distinct half way into the interior, and in some very thin specimens 
they may be seen up to the umbo. Externally they are flat, broad, and striated, with 
a narrow space between them ; they are more distinct on the anterior side and body 
of the shell, as in C. edule, becoming obsolete on the posterior slope, and where the 
exterior is well preserved, they show a sub-imbricated surface all over. In a part of 
the cliff by the river side at Ramsholt, I have found this species in situ with the valves 
united, where they show a very slight gape on the posterior side; the specimens are 
particularly thin and tender, with generally a loss of a considerable part of the exterior ; 
in these specimens the ligament is well preserved. 
