FAMILY COLIMACEA. 73 



11. Helix obvoluta. Obvohite Helix. 

 Shell ; openly umbilicated, flatly discoid, brown qpake, obscurely 

 downy, spire concavely immersed, whorls six, in- 

 creasing slowly, narrowly appressed, densely finely 

 striated, impressed at the suture, last whorl a little 

 descending in front, constricted behind the lip ; 

 aperture small, obtusely triangular, lip reflected, 

 lilac-tinged within, basal and right margins ob- 

 tusely one-toothed within. 

 Helix obvoluta, Miiller (1774), Verm. Hist, part ii. p. 27. 

 Helix holoserica, Gnielin (1788), Syst. Nat. p. 3641 (not of Studer). 

 Helix bilabiata, Olivi (1792), Zool. Adriat. p. 177. 

 Helix trigonophora, Lamarck (1792), Jourri. Hist. Nat. vol. ii. p. 349. 



pi. xlii. f. 2, a, b. 

 Planorbis obvolutus, Poiret (1801), Cog. de VAisne, p. 89. 

 Helicodonta obvoluta, Eisso (1826), Hist. Nat. Europ. Mend. vol. iv. p. 65. 

 Trigonostoma obvolutum, Fitzinger (1833), Syst. Verz. p. 98. 

 Vortex obvoluta, Beck (1837), Ind. Moll. p. 29. 

 Gonostoma obvoluta, Held (1837), Isis, p. 915. 

 Helix (Trigonostoma) obvoluta, Moquin-Tandon (1855), Hist. Moll, vol.ii. 



p. 114. pi. x. f. 26 to 30. 

 Hab. Central Europe. Bare in Britain (among moss at the roots of trees 

 at Ditchain Wood, Hants, and, on the northern side of the chalk 

 escarpment of the South Downs). 

 This very distinct form of Helix is rare in Britain, and doubts are 

 still entertained as to whether it is indigenous. It is unknown in 

 Scotland or Ireland, and has only been found in England at Ditcham 

 and Stoner Hill, in Hampshire, and, according to Forbes and 

 Hanley, for some distance on the northern side of the chalk es- 

 carpment of the South Downs. Throughout France, especially in 

 the northern parts, H. obvoluta is comparatively abundant. It is 

 essentially a Continental type, being represented in a more angularly 

 compressed form by H. angigyra, and in a similar form with the 

 labial teeth more prominently developed by H. holoserica. The 

 animal is described by Forbes and Hanley as being dusky, with 

 the head and neck nearly black. The shell is a closely convoluted 

 discoid with the spire concavely immersed, dark umber-brown in 

 colour, obscurely covered with a fine down. The aperture is cu- 

 riously developed into a compressed angle with indications of teeth 

 on the inner margin. 



