158 Ret?. R. Sheppakd's^ccomw/ 



verified : and it must be allowed that greater changes than this 

 do actually take place betwixt the young and old of many of our 

 land and fresh- water shells. 



33. Helix spirorbis. Trans. Linn. Soc. vol. viii. p. 191. 



In the stream and ditches at Brantham, by the road between 

 Ipswich and Mantiingtree. 



In abundance in the Glebe ponds at Wrabness, Essex. 



A variety sometimes occurs in which the volutions appear as 

 if pressed out from the base towards the vortex ; and being 

 almost disjoined, cause the shell to resemble a little basket. In 

 another variety, and I have found a similar one of Helix vortex, 

 the mouth is enlarged and turned over the preceding volution, 

 which gives the idea of a serpent coiled up. 



This is the shell first distinguished as H. spirorbis by Montagu ; 

 yet it does not answer to the terms albida and pellucida, which 

 Linnaeus uses in his description ; for it certainly has no pre- 

 tension to be called whitish ; nor is it so transparent as Eelix 

 vortex, to which Linnaeus applies the term suhpellucida. Neither 

 will it at all agree with Draparnaud's figure and description of 

 Planorbis spirorbis, which is both albida and pellucida ; for, as 

 he describes his shell supra plana, carina media, anfractu ultimo 

 majore, of course that cannot be the species intended by Lin- 

 naeus. 



35. Helix Draparnaudi. 



H. testa supra subconcava subtus concava subcarinata, anfrac- 

 tibusquatuor transversim striatis : ultimo majore. 



Habitat in aquis dulcibus. 



Testa diametro 3 lin. supra grisea, subtus albida, nitescens ; 



anfractibus quatuor, ultimo, in medio juxta aperturam, sub- 



carinato. Apertura dilatata. 



This 



