158 Rev. R. SHEPPARD'S Account 
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 sPrRoRBIS. Trans. Linn. Soc. vol. viii. p. 191. 
In the stream and ditches at Brantham, by the road between 
Ipswich and Manningtree. 
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 
Linnæus uses in his description; for it certainly has no pre- 
tension to be called whitish; nor is it so transparent as Helix 
vortex, to which Linnæus applies the term subpellucida. 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- 
nzus. : 
35. HELIx DRAPARNAUDI. 
H. testa supra subconcava subtus concava subcarinata, anfrac- 
tibus quatuor 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 
