221 
I have figured a specimen from Peterborough, cast in 
blue Lyas, and encrusted with Pyrites. I have another 
specimen in Cornbrash limestone, from Lechlade, in 
Gloucestershire. I have also a specimen nearly resem- 
bling it, but which may hereafter prove to be a distinct 
species, as it is flatter upon the posterior side, and is 
wider ; it is in a ferruginous sandy limestone, from Kel- 
loways Bridge; a portion of the shell remains upon it : 
it is thick, and is pearly beneath the outer coat. 
These four species of Cardita have been long known by 
the appellation of Heart Cockles, and have been distin- 
guished by their form, and the number of their ridges ; 
both characters are liable to variation, but yet, the four 
species above described, may readily be recognized : it 
would have been fortunate had each been confined to a 
separate stratum. It is impossible to be certain of the 
Genus. 
In Smith’s Stratigraphical System of organized fos- 
sils mention is made of them under the generic name of 
Cardium, first in the Cornbrash, on p. 65, he describes 
the obtusa, and at letter c the lirata ; and refers to them as 
the same that are found in the under Oolite, see p. 104. 
The Cardita producta is refered by him to the Fuller’s 
earth rock. I have seen in Miss Benett’s hands a spe- 
cimen of the C. producta, from the inferior Oolite near 
Bayeux. 
