62 MOLLUSCA FROM THE CRAG. 



6. MODIOLA MARMORATA, Forbes. Tab. VIII, fig. 7. 



MYTILUS DISCORS. Da Costa. Brit. Conch., p. 221, t. 17, fig. 1, 1778. 

 _ Walker and Boys. Test. Min. Rar., pi. 3, fig. 79, 1789. 



Poli. Test. Utr. Sic., vol. ii, p. 211, pi. 32, figs. 15, 16, 1795. 



Donov. Brit. Shells, vol. i, pi. 25, fig. 1, 1799. 



Mat. and Rock. Linn. Trans., vol. viii, p. Ill, pi. 3, fig. 8, 1807. 



Mawe. Conch., pi. 13, fig. 5, 1823. 



W. Wood. Ind. Test., pi. 12, fig. 39, 1825. 

 MODIOLA Turt. Brit. Biv., p. 201, pi. 15, fig. 4, 1822. 



Brown. Illust. Brit. Conch., pi. 29, fig. 10, 1827. 

 S. Wood. Catalogue, 1840. 

 I Gould. Inv. Massach., p. 15, fig. 84, 1841. 



DISCREPANS. Phil, En. Moll. Sic., vol. i, p. 70, 1836. 



Id. - - - vol. ii, p. 50, pi. 15, fig. 11, 1844. 

 Payr. Cat. Moll. Cors., p. 67, 1826. 



EUROP^EA. If Orb. fide Loven. 



TUMIDA. Hanley. Rec. Shells, vol. i, p. 241, pi. 12, fig. 39. 



MARMORATA. Forbes. Malac. Monen., p. 44, 1838. 



Brown. Illust. Brit. Conch., 2d ed., pi. 27, fig. 10. 



Alder. Cat. Moll. North, and Durh., p. 82, 1848. 

 MODTOLARIA Loven. Ind. Moll. Scand., p. 33, 1846. 



CRENELLA Forb. and Hani. Hist. Brit. Moll., vol. ii, p. 198, pi. 45, fig. 4, 1849. 



Spec. Char. Testa minutd, ovato-ellipticd, tumidd, tenui, fragili ; utroque later e 

 striatd, spatio submediano l&vigato vel transverse striato ; umbonibus minimis wbter- 

 minalibus. 



Shell small, ovate or elliptical, tumid, thin, and fragile ; both sides radiatingly 

 striated, with a smooth or rather transversely striated space between them ; umbones 

 small, subterminal. 



Longest diameter, -fths of an inch. 



Locality. Cor. Crag, Sutton. 



Red Crag, Walton Naze. 



Recent, Mediterranean, Britain, Scandinavia, and North America? 



Small specimens and fragments of this species are abundant in the Coralline 

 Crag at Sutton, and it appears to have been one of the commoner shells of that 

 Period. There is no doubt, of this shell being identical with the recent British 

 species, now determined not to be the discors of Linnaeus, a name given to a larger 

 shell (Mytulus impacttts, Herm.} by the Swedish naturalist. 



Our shell in the fossil state has become opaque, but it has retained its nacreous 

 appearance ; it is of an elliptical form, the anterior side being rather broader than the 

 posterior, which is slightly narrowed off from the dorsal slope ; the umbones are small, 

 slightly inflected, with the anterior side projecting a little beyond them, the shell is 

 somewhat regularly tumid, with a very slight flattening on the dorsal portion : the 



