BIVALVIA. 159 



8. CARDIUM DECORTICATUM, S. Wood. Tab. XIV, fig. 1 a d. 



CARDIUM DECOKTICATUM. S. Wood. Catalogue, 1840. 



OBLONGUM. Nyst. Coq. Foss. de Belg., p. 187, pi. xiv, fig. 3, 1844. 



FRAGILE ? Broc. Conch. Foss. Subap., p. 505, t. xiii, fig. 4 a, b. 



Spec. Char. Testa orbiculato-ovatd, obliqud, inaquilaterali, magnd, tumidd, costatd, 

 costis 34 36; latere postico lavigato, ad latere antico costis evanescentibus. 



Shell roundedly-ovate, oblique, inequilateral, large, somewhat tumid, costated, 

 posterior side smooth, ribs becoming obsolete or evanescent on the anterior side. 



Longitudinal diameter, 3 inches ; transverse ditto, 2f inches. 



Localities. Cor. Crag, Sutton, Ramsholt, Sudbourn, Gedgrave. 



This handsome shell is abundant in the Coralline Crag, but it is difficult to obtain in 

 perfection, from its extreme fragility ; the specimens appear not only to have lost much 

 of their animal matter, but the exterior of the younger portion of the shell has become 

 eroded or decorticated down to the base of the ribs, leaving only vestiges of where 

 they had been, while the outer or older part of the shell exhibits the true characters of 

 its original ornament. 



From the description given by M. Nyst, there is every probability that the Belgian 

 shell is identical with our English Crag fossil, but I believe it is quite distinct from the 

 recent C. oUongum, Chemn., and from the Sicilian fossil, as well as from the recent 

 British shell, C. Norvegicum, and also from C. lavigatum, Linn.; in its much more distinct 

 and rugose ribs, it approaches closely in that character the Sicilian fossil, differing, 

 however, from this latter most essentially in its form. 



Card, tenellum, of my Catalogue, is probably the young of this species ; it differs 

 somewhat in outline from the adult shell, having a greater diameter from the anterior 

 to the posterior side, and it was in consequence considered distinct ; but intermediate 

 ages have been since obtained, by which it is thought a specific relationship may be 

 maintained. 



9. CARDIUM INTERRUPTUM, S. Wood. Tab. XIV, fig. 4 a b. 



Spec. Char. Testa rotundato-triangulatd sub-obliqud, in&guilaterali ; costis 35 40 

 depressis, interrupts, ad latum posticum nullis ; margine ventrali serrato. 



Shell roundedly triangular, slightly oblique, inequilateral ; ribs 35 40, depressed 

 and interrupted ; posterior side smooth ; ventral margin denticulated. 



Length, 2j inches ; height, 2 inches. 



Locality. Red Crag, Sutton. 



I have obtained a few specimens only of this species in perfect condition, and 

 these are all of the left valve, but fragments are not particularly rare. 



The rays upon the shell are about forty in number, strongly marked by periodical 

 lines of growth, between which the surface is much eroded or decorticated so deep as 



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