314 PLIOCENE MOLLUSCA. 



Dimensions. — L. 25 mm. B. 16 nun. 



Distribution. — Not known living. 



Fossil : St. Erth. Pliocene : Volhynia (R. Bell). 



Remarks. — This shell, unrecorded as living and only known as a British fossil 

 from St. Erth (where it is fairly common), is closely related to the recent N. 

 mutabilis, Linne, with which it might almost be grouped as a variety. It differs 

 from the latter, however, in size and form, and in certain other particulars stated 

 below, and has been regarded as distinct by all the authors who have dealt with it. 

 I retain Wood's name of N. solida, under which it has been known in our public 

 collections for many years. R. G. Bell states that it occurs in the Pliocene deposits 

 of Volhynia. 



Our fossil approaches to some extent the N. crassilabris of Bellardi. 1 



Nassa mutabilis (Linne). Plate XXXIII, figs. 23 — 25. 



1758. Buccinum mutabile, Linne, Syst. Nat., ed. x, p. 738, no. 398. 



1814. Buccinum mutabile, Brocchi, Conch, foss. subap., vol. ii, p. 341, pi. iv, fig. 18. 



1836-43. Buccinum mutabile, Philippi, Eiium. Moll. Sic, vol. i, p. 222, 1836 ; vol. ii, p. 189, 1843. 



1870-98. Nassa mutabilis, A. Bell, Journ. de Conch., vol. xviii, p. 345, no. 199, 1870; Proc. Roy. 



Irish Acad. [3], vol. ii, p. 626, 1893 ; Trans. Roy. Geol. Soc. Cornwall, vol. xii, p. 139, pi. i, fig. 4, 



1898. 

 1873-5. Nassa mutabilis, Seguenza, Boll. R. Com. Geol. Ital., vol. iv, p. 300, no. 139, 1873; vol. vi, 



p. 276, no. 255, 1875. 

 1882. Nassa mutabilis and vars., Bucquoy, Dautzenberg et Dollfus, Moll. mar. Rouss., vol. i, p. 42, 



pi. x, figs. 3 — 7. 

 1882. Nassa mutabilis and vars., Bellardi, Moll. Terr. Terz. Piem., pt. iii, p. 24, pi. i, figs. 20, 21. 

 1882. Nassa mutabilis and var. Companyoi, Fontanues, Moll, plioc. Vail, du Rhone, vol. i, p. 70, pi. v, 



figs. 14 — 16. 



1885. Nassa mutabilis, S. V. Wood, Quart. Journ. Geol. Soc, vol. xli, p. 68. 



1886. Nassa mutabilis, Kendall and R. G. Bell, Quart. Journ. Geol. Soc, vol. xlii, p. 210. 



1887. Nassa mutabilis, Kobelt, Icon, schalentrag. europ. Meeresconcb., vol. i, p. 122, pi. xxi, figs. 5 — 

 24 ; pi. xxii, figs. 1 — 14. 



1890. Nassa mutabilis, Carus, Prod. Faun. Medit., vol. ii, p. 391. 



1890-1904. Nassa mutabilis and vars., Sacco, Boll. Soc. Geol. Ital , vol. ix, p. 208, nos. 2536 — 40, 



1890 ; Moll. Terr. Terz. Piem., pt. xxx, p. 63, pi. xv, figs. 26—29, 1904. 

 1890. Nassa mutabilis, C. Reid, Plioc. Dep. Brit., p. 248. 



1892. Spliieronassa mutabilis, Locard, Coq. mar. Cotes de France, p. 74, fig. 61. 

 1901. Nassa mutabilis, Cossmann, Ess. Palcoconch. compar., vol. iv, p. 210, pi. ix, figs. 1, 2. 

 1901-7. Nassa mutabilis, Scalia, Att. Accad. Gioen. Sci. Nat. Catania [4], vol. xiv, p. 14, no. 175, 



1901 ; vol. xx, p. 35, no. 312, 1907. 

 1911. Nassa mutabilis and vars., Cerulli-Irelli, Palaeont. Ital., vol. xvii, p. 244, pi. xxii, figs. 17 — 24. 

 1913. Nassa mutabilis, Gignoux, Ann. Univ. Lyon, n.s. [1], vol. xxxvi, p. 504. 



Specific Characters. — Shell oval, oblique; whorls 7, convex, depressed above, 

 the last more or less inflated, much the largest ; spire short, rapidly diminishing 

 1 Moll. Terr. Terz. Piem., pt. iii, p. 23, pi. i, fig. 18. 



