168 MOLLUSCA FROM THE CRAG. 



1. FISSURELLA GR.ECA. Linn. Tab. XVIII, fig. 4, a c. 

 PATELLA GR^ECA. Linn. Syst. Nat. p. 1262, 1766. 



CANCELLATA. Lister, t. 527, fig. 2, 1685. 



GR^CA. Mont. Test. Brit. p. 492, 1803. 



APERTURA. p. 491, t. 13, fig. 10. 



RETICULATA. Don. Brit. Shells, t. 21, fig. 3. 

 FISSURELLA GR^CA. J. Sow. Min. Conch, t. 483, 1826. 



Brown. Illust. Brit. Conch, pi. 36, fig. 10-11, 1827. 



SYPHO RADIATA. pi. 36, fig. 20. 



FISSURELLA GR^CA. Flem. Brit. An. p. 364, No. 362, 1828. 



APERTURA. - No. 363. 



GIUECA.. Nyst. Coq. foss. de Belg. p. 353, pi. 35, fig. 7, 1844. 



CANCELLATA. S. Wood. Catalogue 1842. 



Morris. Catalogue of Brit. Fossils, 1843. 



F. Testa ctypeiformi, oblongo-ovatd, depresso-conicd ,- costis valde elevatis, lineisque 

 transversis cancettatis, ad intersectiones tuberculatis ; foramine ovato ; margine crenulatd. 



Shell shield-shaped, or oblon go-ovate, covered with elevated rounded rays, decus- 

 sated by the thickened or slightly reflected lines of growth ; aperture oval, thickened 

 within, and rather contracted in the middle ; vertex truncated, or sloping towards the 

 anterior margin ; margin slightly thickened and crenulated. 



Longest diameter, \\ inch. 



Locality. Cor. Crag, Sutton and Ramsholt. 



Red Crag, Sutton, Bawdsey, Newbourn, and Walton. 



Recent, British Seas. 



Young specimens of this shell are abundant in the Coralline Crag, in which the 

 involute vertex is remaining, but I have not seen this inflected portion on any shell 

 which has attained the length of one quarter of an inch. This species is subject to much 

 variation in form, but the posterior portion is always broader, as well as longer, than 

 the anterior ; sometimes the shell is a good deal elevated, and the sides of the cone 

 convex ; in others it is depressed, with the sides flat, inclining to concavity, from the 

 vertex to the margin, which is a little thickened and crenulated. The rays generally 

 alternate, one large and one small, though sometimes they are placed in sets, each 

 fifth one being more elevated than the others. Fig. 4 c is the young state of this shell. 

 This is given as an Eocene fossil, by M. Deshayes, from Grignon. 



