PLANORBIS. 159 



Northumberland or Cornwall. Dumfriesshire (Dr. John- 

 ston and Sir William Jardine) ; Aberdeenshire (Mac- 

 gillivray) ; near Dublin (W. Thompson). 



P. spirorbis, Linnaeus. 



Extremely depressed ; whorls very narrow and of very slow 

 increase ; angulation of the periphery not acutely prominent ; 

 both disks concave ; mouth not angulated. 



Plate CXXVII. fig. 9, 10. 



Helix spirorbis, Linn. Syst. Nat. ed. 12, p. 1244. — Mont. Test. Brit. p. 455; 

 Suppl. pi. 25, f. 2. — Maton and Rack. Trans. Linn. Soc. 

 vol. viii. p. 191.— Rack. Dorset Catalog, p. 53, pi. 20, f. 17.— 

 Turt. Conch. Diction, p. 47. — Dillw. Recent Shells, vol. ii. 

 p. 907.— Wood, Index Testae, pi. 33, f. 50. 



Planorbis „ Muller (not Drap.) Venn. Hist. vol. ii. p. 161. — Fleming, 

 Brit. Amm. p. 277. — Turt. Manual L. and F. W. Shells, 

 p. 115, f. 98. — Alder, Trans. Nat. Hist. Soc. Northumb. 

 vol. ii. p. 338. — Gray, Manual L. and F. W. Shells, p. 268, 

 pi. 8, f. 98.— Brown, Illust. Conch. G. B. p. 33, pi. 14, f. 42, 

 43.— Brard, Coq. Envir. Paris, p. 156, pi. 14, f.42, 43.— C. 

 Pfeif. Deutsch. L. und Siissw. Moll. pt. 1, p. 79, pi. 4, f. 8. 

 — Lam. Anim. s. Vert. (ed. Desh.) vol. viii. p. 385. — Nilss. 

 Moll. Suec. Ter. et Fluv. p. 78. — Rossmassl. Iconog. Land 

 und Siissw. Moll. pt. 1, p. 106, pi. 2, f. 61. — Cantr. Mem. 

 Ac. Brux. vol. xiii. p. 166. 

 „ vortex, var. b. Drap. Moll. Ter. et Fluv. France, p. 45, pi. 2, f. 6, 7. — 



Macgilliv. Moll. Aberd. p. 117. 

 „ leueostomus, Michaud (as of Millet) Comp. Drap. Moll. France, p. 80, 

 pi. 16, f. 3, 4, 5 (teste Thompson, from type). 



Shell very closely resembling vortex, yet scarcely so com- 

 pressed, and with both disks concave. The whorls, which 

 on the inferior disk are much less flattened than in the 

 preceding species, are less thin and transparent, often of a 

 rusty brown, peculiarly narrow, and of still slower in- 

 crease : the wrinkles are nearly obsolete. The body, like- 

 wise, is nearly equally broad above and below, and its 

 shelve being more abrupt and rounded, the basal angula- 



