152 LIMOSAD/E. 



P. nautileus, Linnaeus. 



Very small, usually with membranaceous ridges ; periphery 

 angulated ; mouth entire, rounded-oval. 



Plate CXXVI. fig. 6, 7. 



Helix Nautileus, Linn. Syst. Nat. ed. 12, p. 1241. — Mont. Test. Brit. p. 464, 



pi. 25, f. 5. 

 Planorbis imbricatus, M tiler, Hist. Verm. pt. 2, p. 165. — Jeffreys, Trans. 

 Linn. Soe. vol. xvi. p. 388. — Turt. Manual L. and F. 

 W. Shells, p. Ill, pi. 8, f. 94.— Gray, Manual L. and 

 F. W. Shells, p. 261, pi. 8, f. 94. — Brown, Illust, 

 Conch. G. B. p. 31, pi. 14, f. 46, 47, and pi. 18, f. 10.— 

 Drap. Moll. Ter. et Fluv. France, p. 44, pi. 1, f. 4.9, 50, 

 51.— Brard, Coq. Paris, p. 163, pi. 6, f. 10, 11.— 

 Lam. Anim. s. Vert. (ed. Desh.) vol. viii. p. 389. — 

 C. Pfeif. Deutsch. Land und Siissw. Moll. pt. 1, p. 80. 

 pi. 4, f. 15, 16. — Nils. Moll. Suec. Ter. et Fluv. p. 76. 

 — Hartm. in Sturm. Deutsch. Fauna, pt. 7, pi. 14. — 

 Kickx, Moll. Brabant, p. 67. — Mermet, Moll. Pyren. 

 p. 59. 

 „ cristatus, Drap. Moll. Ter. et Fluv. France, p. 44, pi. 2, f. 1, 2, 3.— 

 Hartm. in Sturm. Deutsch. Fauna, pt. 7, pi. 13. — Mermet, 

 Moll. Pyren. p. 60. 

 Turbo Nautileus, Maton and Rack. Trans. Linn. Soc. vol. viii. p. 169, pi. 5, f. 4. 

 — Rack. Dorset Catalog, p. 50, pi. 19, f. 16. — Tirt. Conch. 

 Diction, p. 227, f. 78.— Woon, Index Testae, p. 32, f. 162.— 

 Dillw. Recent Shells, vol. ii. p. 882. 

 PlanorbU Nautilus, Fleming, Brit. Anim. p. 278. 



„ Nautileus, Dupuy, Moll. Gers, p. 51. — Stein, Schnecken Berlins, pi. 2, 

 f. 24.— Walker, Testae. Minut. Rariora, f. 20, 21. 



Shell very small, much depressed, very fragile, not lus- 

 trous, of a slightly olivaceous horn-colour, often invested 

 with a black incrustation, adorned for the most part (for 

 occasionally they are obsolete) with distant subimbricated 

 longitudinal membranaceous rings, or ridges, which are 

 usually more marked on the lower disk, and serrate the 

 periphery by their projection as vaulted scales. AVhorls 

 three, very rapidly developed, profoundly divided, more 

 convex on the lower disk, which is umbilicately hollowed. 



