116 On the Land and Fresh Water Mullusca 



the muddy margin of the river Wye, four miles from its junction 

 with the Severn, generally out of the water, but within tide-way. 

 Its habits are somewhat similar to those of some species of Limneus ; 

 indeed, a little further up the same river, nearly opposite Tintern, 

 its place is taken by the small variety of L. palustris before-men- 

 tioned as common in such situations. 



Fam. Ancylidje, (Ancylea, Mencke.) 

 Gen. 21. Ancylus, Geoffroy. 



1. Fluvia tills, Mull. 



2. Lacustris, Mull. 



Ord. Pectinibranchia. (Pectinibranches, Cuv.) 



Fam. TuRBiNiDiE. (Les Sabots, Cuv.) 



Gen. 22. Paludina, Lamarck. 



1. Vivipara, Linn., Lam. 



2. Achatina, Drap., Lam. 



3. Impura, Drap., Lam. 



4. Similis, Drap. 



5. Analina, Drap. Mich. 



This species has been found in Greenwich marshes by J. E. Gray, 

 Esq. to whom I am indebted for specimens. Though living so far 

 inland, it appears to belong to a littoreal genus, rather than to Pa- 

 ludina, from which it differs in having a spirally grooved operculum. 



Cyclostoma acutum, Drap. (Paludina muriatica, Lam.*) is now 

 well known to be a marine species, allied to Turbo Ulvae of English 

 writers, and abundant on many of our sandy coasts. P. Viridis of 

 Turton's Manual I take to be the young of P. similis, judging from 

 specimens in Mr Clark's cabinet. His P. stagnorum is probably a 

 more slender variety of the same ; but in the absence of specimens 

 it is impossible to decide. Dr Turton does not give any localities 

 for either of these species. 



Gen. 23. Assiminea, Leach. 

 1. Gray ana, Leach. 



Allied to the littoreal tribes. 



Gen. 24. Valvata, Muller. 

 1. Piscinalis, Mull., Lam. 



Var. V. depressa, Pfeiffer. 



* Lamarck refers his P. muriatica to C. anatinum, Drap., but I follow Ferus- 

 sac in considering it to be the C. acutum. Michaud places these two in a se- 

 parate division of the genus, which he calls " Especes des eaux saumatres." 



