BIVALVIA. 151 



Diameter, 4^ inches. 



Localities. Britain : Bracklesham, Bramshaw, Brook, Stubbington, Selsey, Alum 

 Bay {Edwards). Bagshot and Hawley {flde B. Jones). 

 Prance: Sables inferieurs, Calcaire grossier, Sables moyens {Deshayes), 



Faluns de Touraine? {Desk.). 

 Belgium : Gand, Lovain, &c. {Nt/st). 

 North America: Claiborne, Alabama {Conrad). 



This species is abundant in individuals, and may be obtained, of all ages and all sizes, 

 on the beach at Bracklesham. M. Deshayes speaks of it as also abundant in France, where 

 it is disseminated through a series of deposits. I have never seen it from Barton. It is 

 a very handsome shell, and its great solidity has been favourable to its preservation. 



The interior of the shell in aged specimens is often much thickened, by which means 

 the impressions of the adductors are deeply seated. This animal has also left two small 

 distinct, and deep impressions by the pedal muscles, the one above the oral, the other over 

 the anal adductor, indicating, probably, the possession of a large and falcated foot. The 

 hinge is variable ; in some specimens it is very thick, with an elevated umbo, in others it 

 is correspondingly depressed, with a narrow hinge-line, and the contour of the shell is 

 very variable, some specimens being considerably higher than they are long, while others 

 have the length greater than the height. 



In the young state the ribs are generally more or less rounded, but they become flat 

 with the increase of age, and in old specimens the ribs are almost obliterated at the outer 

 edge ; they vary in number from twenty-seven to thirty. 



This is one of those species possessing a wide geographical range. Sir Charles 

 Lyell gives it as a species from Coggins Point, on the James Uiver, below Richmond, in 

 America (' Proc. Geol. Soc.,' vol. iv, p. 564, 1845), and says it cannot be distinguished 

 from one of the common varieties of the European shell. Mr. Conrad speaks of his shell 

 as having twenty-two ribs. 



15. Cardita simplex, Edwards, MS. Tab. XXI, fig. 4, 



Sj)ec. Char. C. Testa crassd, suborbiculatd, convexd, inaqidlaterali, radiatim costatd, 

 costis circa 15, angustis, distantibus, simplicibtis, interstitiis latis, Icevigatis ; umbonibus 

 prominulis ; lunula minima elongatd ; cardine crassiusculo. 



Shell thick, suborbicular, convex, inequilateral, with about 15 radiating ribs, sub- 

 angular, thin, and distant, spaces between them broad and smooth ; beaks slightly 

 elevated, lunule small and elongated, hinge moderately thick. 



Diameter, \ an inch. 



Locality. Roy don {Edwards). 



This does not appear to be abundant. Its principal distinction is in the character of 



