158 BRITISH MOLLUSKS. 



Lymncea Boissii, Dupuy (1851), Hist. Moll. vol. v. p. 479. pi. xxv. f. 9. 



Lymncea teres, Bourguignat (1853), Voy. Mer Morte, p. 58. 



Lymncea fGulnaria) ovata and limosa, Moquin-Tandon (1855), Hist. Moll. 



vol. ii. p. 465 to 470. pi. xxxiv. f. 11 to 16. 

 Hob. Throughout Europe. Siberia. Thibet. Afghanistan. (In ponds, 



lakes and ditches, and in springs at various elevations.) 



Water snails, as we have already remarked, are distributed over 

 the globe, with less variation of typical character than land snails. 

 Lymnea limosa, more generally known to collectors by the name 

 peregra than by its Linnean name, is perhaps the most abundantly 

 and widely diffused of all our mollusks. It is the common pond 

 snail both of the Germanic and Lusitanian regions of Europe, it 

 ranges over Western Asia from Siberia to Afghanistan and Thibet, 

 and it is so nearly approached in the United States by Mr. Say's 

 L. catascopium that doubts are entertained whether the two alleged 

 species are really distinct. It has also a near representative in 

 Greenland in L. Vahlii. The shell of L. limosa is yellowish horn- 

 colour, generally of a uniform tint, but it is extremely variable in 

 form. The variability is, however, clearly a modification of the 

 same specific type. There is no fear of mistaking the most widely 

 inflated form of IJ. limosa for L. auricularia. All the numerous 

 variations of the species arise simply out of a more or less elongately 

 spired plan of convolution ; the remaining differences follow in 

 the order of correlation of growth. Where the spire is shortest, as 

 in the variety which has been named L. JEturnettii, the whorls are 

 most inflated ; where it is longest, as in a Thibetan variety named 

 L. Hoolceri, they are the most restricted in diameter. 



The animal of L. limosa varies chiefly in colour. It is described 

 by different observers as being dark-grey or brown, or greenish- 

 brown or olive-yellow, mottled with grey or black, and sometimes 

 speckled with opake yellow or white. The tentacles are flatly tri- 

 angular, broad at the base, with the eyes, small clear and bright, 

 between them. Sometimes the body and shell are convoluted 

 sinistrally ; it is however the exception, not as in Physa the rule, 

 of growth. Specimens in this state Mr. Metcalfe informs me he 

 once collected in the neighbourhood of Scarborough, but never 

 in any other locality. The largest specimens he ever found of 

 L. limosa of the regular dextral growth were in some ponds on the 

 north side of Hampstead Heath. 



