QOI^CEYLIA—DITHYRA. 41. 191 



Da Costa, p. 178, tab. 13, fig. 6. 



Donovan, British Shells, ii. tab. 54. 



Montagu, Test. Brit. p. 80. 



Linn. Trans, viii. p. 65. 



Turton, British Fauna, p. 152. 



Dorset Catal. p. 31, tab. 7. fig. 6. 



Wood, Conch, p. 222, tab. 54, fig. 1. 



Dillwyn, Descript. Catal. p. 123. 



Turton, Conch. Diet. p. 3J. 



Chemnitz, vi. p. 191, tab. 18, fig. 185, 186. 

 Pectunculus subfuscus. Lister, Conch, tab. 332, fig. 169. 

 Mus. nost. English and Irish coasts. 



Shell growing to two inches and a half long, and two inches 

 broad, covered with a brownish-olive glossy skin, often marbled with 

 white and various hues of red, with very obscure longitudinal striae 

 and remote transverse ones, flattish and much produced on one side 

 where the striated marks become totally obliterated. 



This shell, in its decay, offers a good exemplification of the re- 

 mark of Brard, in his note on the Succinea amphibia, p. 75, that 

 many species, after long exposure to the air in a dead state, become 

 thickened in their substance, either generally or partially ,• occasion- 

 ed, as he supposes, by a sort of relaxation in their testaceous tex- 

 ture ; or probably by the absorption of oxygen, and their gradual 

 conversion into lime : and in this manner he accounts for the thick- 

 ness and distortion of most fossil shells. 



We have in our cabinet some specimens, which appear to have 



