PLANORBIS. 157 



usual, with the gyration rather more compact, less concave 

 on the upper disk, profoundly hollowed in the centre of 

 the lower one : the keel being indistinct, the aperture 

 which projects below rather than above is suborbicular. 

 The form Draparnaldi somewhat resembles it, but is pallid, 

 small, and with the keel more central. 



The animal is entirely dusky, almost black ; the tenta- 

 cles have dark centres and pale linear bases ; the foot is 

 thick and obtuse. 



This species in most districts is the commonest of the 

 genus, and is very widely diftused through almost all parts 

 of the British Islands; so general, that any list of locali- 

 ties would be superfluous. It is absent, however, from 

 Professor Macgillvray's Aberdeenshire catalogue. It is 

 widely diffused on the Continent. 



P. VORTEX, Linnaeus. 



Extremely depressed ; whorls narrow and of slow increase ; the 

 two disks not concave together ; periphery gradually carinated, 

 mouth not angulated. 



Plate CXXVII. fig. 6, 7, 8. 



Helif vortex, Linn. Syst. Nat. ed. 12, p. 1243.— Penn. Brit. Zool. ed. 4, vol. iv. 

 p. 133, pi. 83, f. 124. — PuLT. Hutchins, Hist. Dorset, p. 47.— 

 DoNov. Brit. Shells, vol. iii. pi. 75. — Mont. Test. Brit. vol. ii. 

 p. 454; Suppl. pi. 25, f. 3. — Maton and Rack. Trans. Linn. 

 Soc. vol.viii. p. 189.— Rack. Dorset Catal. p. 52, pi. 20, f. 12. - 

 TuRT. Conch. Diction, p. 46. — Dillw. Recent Shells, vol. ii. 

 p. 914.— Wood, Index Testae, pi. 33, f. 40. 



PUnioihis „ MuLLER, Verm. Hist. pt. ii. p. 158, var. a. — Jeffreys, Trans. 

 Linn. Soc. vol. xvi. p. 382; Manual L. and F. W. Shells, p. 109, 

 f. 91.— Gray, Manual L. and F. W. Shells, p. 2G7, pi. 8, f. 91. 

 — Thompson, Ann. Nat. Hist. vol. vi. p. 125. — Macgilliv. 

 Moll. Aberd. p. 114 (probably). — Brown, Illust. Conch. G. B. 

 p. 32, pi. 14, f. 44, 45.— Drap. Moll. Ter. et Fluv, France, p. 44, 



pi. 2, f. 4, 5. — Brard, Coq. Envir. Paris, p. 154, pi. 6, f. 8, 9 



VoiTH in Sturm. Deutsch. Fauna, pt. 4, pi. 6. — C. Pfeif. 

 Deutsch. Land und S'ussw. Moll. pt. 1, p. 79, pi. 4, f. 7. — Nilss. 



