142 EOCENE MOLLUSCA. 
present very considerable variation in regard to magnitude. C. planicosta measures 
5 inches in diameter, while C. atomus is, according to M. Deshayes, only 1 millimetre in 
diameter ; but they all possess considerable solidity. 
1. Carpita acuticostata? Lamarck. Tab. XXII, fig. 5, a, 6. 
VENERICARDIA acuTiIcosTatTa (?), Lamarck. An. du Mus,, t. vii, p. 57, No. 4, 1807. 
— — Desh. Coq. foss. des Env. de Par., t. 1, p. 153, pl. 25, 
figs. 7, 8, 1825. 
CaRDITA ~ Nyst. Coq. foss. de Belg., p. 208, pl. 16, fig. 6 ? 1843. 
— — J. Sow. In Dixon’s Geol. of Sussex, p. 92, 1850. 
— _ Desh. An. sans Vert. du Bass. de Par., t.i, p. 760, 1858. 
CaRDIUM SERRIGERUM, Lamarck. An. sans Vert., t. vi, p. 19, No. 8, fide Desh., 1819. 
Spec. Char. “C. Testd subrotundd, tumidd, cordiformi, subobliqud, crebricostata, 
costis angustis, angulatis, squamoso-serratis, anticis duplicatis.” (Deshayes.) 
Shell suborbicular, tumid, heart-shaped, slightly oblique, costated ; ribs narrow, angu- 
lated with squamose tubercles. 
Diameter, ths of an inch. 
Locality. Bracklesham (Hdwards). 
France : Chaumont, Grignon, Parnes, Courtagnon (Deshayes). 
Belgium: Aeltre, prés de Bruges (JVys?). 
Asia Minor, sec. Deshayes: Egypt, fide Bellardi. 
M. Deshayes, as above referred to, speaks of this species as a British fossil, but as 
differmg from the French shell in the number of costa. He observes, ‘‘ Dans l’espéce 
d’ Angleterre ces cOtes sont au nombre de vingt seulement ; on en compte trente, quelque- 
fois trente deux dans lacuticostata.” Our shell has 24 to 26 costz, and appears to 
correspond better with the Belgian fossil of that name, which is said to have 26. The 
cost upon our specimens are more or less imbricated all over, but especially so on those 
in the pedal region. The ribs have a central keel, and there is a faint ray on each side, 
dividing the rib, as it were, into four parts, two on each side of the central keel. This 
appears to differ from C. carinata of Min. Conch.’ in being less elongated, and in the ribs 
being more regularly nodulous. 
Fig. 11, Tab. XXII, represents a specimen from Bramshaw; it has on the tablet 
the MS. name of C. asperrima. It is intermediate between acuticostata and carinata, 
but is not, I think, sufficiently distinct to form a species of itself, but an abnormal form, 
and for the present it is placed as a var.—C. acuticostata, var. asperrina. 
