84 MOLLUSCA FROM THE CRAG. 



3. Nucula tenuis, Montague. Tab. X, fig. 5, a — b. 



Arca tenuis. Mont. Test. Brit. Suppl., p. 56, t. 29, fig. 1, 1808. 



— — Pennant. Brit. Zool., vol. iv, p. 218, fide Gould. 



— — Dillw. Desc. Cat. Rec. Shells, p. 246, 1817. 



— — Turt. Conch. Diet., p. 11, 1819. 



— — W. Wood. Ind. Test., Arca, p. 47, pi. 10, fig. 45, 1825. 

 Nucula tenuis. Turt. Brit. Biv., p. 177, 1822. 



— — Flem. Brit. Ann., p. 402, 1828. 



— — Brown. Illust. Conch. Gr. Brit., pi. 25, fig. 13, 1827. 



— — Gould. Inv. Massach., p. 105, fig. 64, 1840. 



— — Moller. Ind. Moll. Groen., p. 17, 1842. 



— — Mac Gill. Moll. Aberd., p. 244, 1843. 



— — Morris. Cat. Brit. Foss., p. 95, 1843. 



— — Thorpe. Brit. Mar. Conch., p. 105, 1844. 



— — Forbes. Geol. Surv., vol. i, p. 83, 1842. 



, . — — Hanley. Rec. Shells, vol. 1, p. 171, pi. 10, fig. 45. 



— — Alder. Cat. Moll. North, and Durh., p. 79, 1847. 



— — Loven. Ind. Moll. Scand., p. 34, 1846. 



— — Forb. and Hani. Hist. Brit. Moll., vol. ii, p. 223, pi. 47, fig. 6 (Animal), 



pi. P, fig. 5, 184 9. 



— tenera. S. Wood. Mag. Nat. Hist., New Series, vol. iv, p. 295, pi. 14, fig. 2, 



— Ryckholtiana ? Nyst. Coq. Foss. de Belg., p. 233, pi. 15, fig. 10, a— b, 1844. 



— decipiens. Phil. En. Moll. Sic, vol. ii, p. 48, t. xv, fig. 15, 1844. 



— lucida. Blanding. MSS. fide Gould. 



Spec. Char. Testa ovatd, trigono-ellipticd, lavigatd, tenui, latere antico subangulaio ; 

 lunula parum distinctd, margine ventrali arcuato, integro. 



Shell ovate, elliptically triangular, smooth, and thin; anterior side produced, 

 roundedly angular ; lunule not well defined, ventral margin smooth. 



Diameter, \ an inch. 



Locality. Cor. Crag ? Gedgrave. 

 Red Crag, Bawdsey. 

 Mam. Crag, Bridlington, Chillesford. 



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



Two specimens of a species resembling this are in my Cabinet, they were obtained 

 from the Coralline Crag, but are too imperfect for correct determination. In the 

 Red Crag Formation it has undoubtedly made its appearance, several individuals were 

 found by myself, and in the sandy deposit at Chillesford it is an abundant shell 

 seemingly increasing in numbers towards the present Period. Its greater tenuity and 

 more ovate form will distinguish this from N. nucleus, as well as the absence from the 

 margin of all crenulations. It differs from the young of N. laevigata in being less 

 transverse, that species having a greater diameter when measured from the anterior 

 to the posterior margin, the hinge line also forms a greater angle than in tenuis, and 

 the posterior termination is somewhat produced. In this species the anterior dorsal 

 margin is more rounded than in any of the others, so is the ventral margin, 



