188 BRITISH MOLLUSKS. 



1. Bythinia similis. Bike Bythinia. 



Shell ; very small, conically ovate, minutely umbilicated, fulvous 



horny, semitransparent, whorls five to 



six, convex, smooth, channelled at (\ 



the sutures, aperture obliquely ovate, 



columellar lip thinly callously re- 

 flected. Operculum horny, of two 



whorls, nucleus lateral. 

 Cyclostoma simile, Draparnaud (1805), Hist. 



Moll. p. 34. pi. i. f. 15. 

 Valvata similis, Hartmann (1821), Syst. Gast. 



p. 57. 

 Paludina similis, Micliaud (1831), Comp. de Drap. p. 93. 

 Bythinia similis and Moutonii, Dupuy (1849), Cat. Ewtram. p. 45 and 48. 

 Hydrobia similis, Dupuy (1851), Hist. Moll. vol. v. p. 552. pi. xxvii. f. 9. 

 Rissoa anatina, Forbes and Hanley (1853), Hist. Brit. Moll. vol. iii. 



p. 134. pi. lxxxvii. f. 3, 4 (not Cycl. anatium, Drap.). 

 Bythinia (Bythinella) similis, Moqtrin-Tandon (1855), Hist. Moll. vol. ii. 



p. 526. pi. xxxix. f. 18, 19. 

 Hah. Central and Southern Europe. Corsica. Siberia. England. (In 



ditches near the Thames at Greenwich.) 

 This is the little mollusk referred to by Mr. Jeffreys in the 

 ' Annals of Natural History' for 1855, under the name Littorina (?) 

 anatina, when speaking of the habitat, in muddy ditches, occasion- 

 ally overflowed by the tide, on the banks of the Thames between 

 Greenwich and Woolwich, of Assiminea G-rayana. Along with 

 the general characters of Bythinia it has the few-whorled oper- 

 culum of its associate Assiminea. Moquin-Tandon refers it on 

 this account to a subgenus, Bythinella, together with nine other 

 similarly opercidated species, natives of France; and Dupuy places 

 it in Hartmann's genus Hydrobia, as lately adopted by Mr. Jeffreys. 

 G-erstfelclt, while adopting the genus Hydrobia for a new Siberian 

 species, H. Angarensis, retains the present in Bythinia. 



The animal is described as being of a dark grey or fulvous brown 

 hue, speckled with white. The shell is distinguished by its very 

 small size and channelled suture. M. Moquin-Tandon describes it 

 as being widely diffused in France, chiefly in the vicinity of the 

 Pyrenees, and extending southwards to the island of Corsica. Its 

 appearance in Siberia leads to the conclusion that it is pretty 

 generally diffused throughout the Continent. 



