of Great Britain. 117 



Specimens of V. depressa, Pf. were sent me from Lancashire some 

 years ago by Mr Kenyon. They are exactly similar to those in 

 Ferussac's cabinet, received from Pfeiffer himself ; but it can scarce- 

 ly be considered more than a variety of V. piscinalis. 



2. Cristata, INIull. 

 V. spirorbis, Drap. 



Dr Turton has introduced two other species, V. planorbis. Drap. 

 and V. minuta, Drap. into his Manual, but no specimens of them 

 are now to be found in his cabinet. I took some pains to investigate 

 these two species when in Paris. On examining three of the prin- 

 cipal collections there, those of the Jardin des Plantes, the Baron de 

 Ferussac, and the Prince Rivoli, in the latter only I found any- 

 thing under the name of V. planorbis. The specimens were V. 

 cristata, Mull. M. de Ferussac had specimens under the name of 

 V. minuta from two different individuals. Those from Pfeiffer are, 

 I think, the young of V. cristata ; and the others (I forget from 

 whom, but with the name of Draparnaud,) the young of V. piscina- 

 lis. Mr Miller introduced V. minuta into his Catalogue of the Land 

 and Fresh water Shells of the environs of Bristol, but no specimen 

 of it is preserved in the Bristol Museum. Dr Turton says that his 

 V. minuta is the Helix serpuloides of Montagu. This is well known 

 to be a marine shell, referable to the genus Skenea of Fleming. Mr 

 Thompson of Belfast has, however, favoured me with the examina- 

 tion of a shell, which may possibly turn out to be the V. minuta, 

 Drap., though I suspect it to be marine. 



Fam, NERiTiDiE, Turt, (Les Ncrites, Cuv.) 

 Gen. 25. Neritina, Lamarck. 

 1. Fluviatilis, Lin. Lam. 



MSedion. MOLLUSCA ACEPHALA,Fer. (LesAcephales,Cuv.) 



C/a5,y.— CONCHIFERA, Lam. (Acephales testaces, Cuv.) 



Ord. — Lamellibranchia. (Lamellibranches, Cuv.) 



Fam — Mytilid^. (Les Mytilaces, Fer.) 



Gen. 26. Dreissena, Vanbeneden. 



1. Polymorpha, Pallas, Vanb. 



This species, being found in three localities in England, and one 

 in Scotland, seems now to have regularly established itself in our 



Fam. NAiADiE. (Les Nayades, Fer.) 

 Gen. 27. Anodon, Oken. (Anodonta, Lam.) 

 \. Cygnaeus. Lin. Lam. 

 VOL. II. NO. 8. I 



