112 LIMNiEID^. 



Var. 3. lahiata. Shell dwarfed and more solid, with the 

 outer lip much reflected and thickened. L. 0*9. B. 0*55. 



Var. 4. sinistrorsa. Spire reversed. 



Habitat : Slow rivers, marshes, and standing water 

 throughout the kingdom; but it is more local than L. 

 peregra. Var. 1. Kennet and Avon Junction Canal, 

 Wilts (Montagu) ; Surrey and Croydon Canal (Leach) ; 

 R. Cam at Cambridge (Granger) ; Grand Canal, Dublin 

 (Warren). This variety is the Stagnicola elegans of 

 Leach. Var. 2. From the last-mentioned locality. Var. 3. 

 Lough Neagh, Ireland (Moggridge). Var. 4. Kenn Moor, 

 Somerset (Norman). This species is one of our upper 

 tertiary fossils. It ranges from Siberia to Naples. 



This mollusk is sluggish, but fond of floating. Before 

 descending to the bottom it withdraws its body into the 

 shell, and in so doing disengages the air from its pouch, 

 which escapes with a perceptible noise. The shell is 

 remarkably handsome ; but it is often disfigured by a 

 coating of vegetable or calcareous matter. The outer 

 lip sometimes becomes thickened in consequence of a 

 temporary cessation of growth ; and in such cases vari- 

 cose marks are observable on the spire at intervals. 

 Young shells are extremely slender, and the mouth is 

 not expanded as in adult specimens. In this state they 

 somewhat resemble L. glabra in form, and might be 

 mistaken for a new species. Miiller tried the experi- 

 ment of cutting oflP the heads of some of this kind of 

 mollusk to see if they would be reproduced ; but he tells 

 us that the poor animals did not long sur^dve the opera- 

 tion. Menke supposed that the shell of this species was 

 the helmet of the Frogs in Homer^s ^ Batrachomyo- 

 machia^; but, in opposition to this ingenious idea, it may 

 be remarked that the L, stagnalis does not appear to 



