168 MOLLUSCA FROM THE CRAG. 



1. Fissueella GKJ3CA. Linn. Tab. XVIII, fig. 4, a — c. 

 Patella gr£:ca. Linn. Syst. Nat. p. 1262, 1766. 



— cancellata. Lister, t. 527, fig. 2, 1685. 



— gr/ECA. 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. 



— GR,ECA. 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 clgpeiformi, oblong o-ovatd, depresso-conicd ; costis valde elevatis, lineisque 

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



Shell sliield-sliaped, or oblongo-ovate, covered with elevated rounded rays, 

 decussated 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. 



