LIMN^US. 255 



L. stagnaUs is light, has the last whorl and tlie aperture 

 much inflated, and the spire elegantly tapering. These 

 are rather large shells, but the shell of 



L. glaher is small, light-coloured, and cylindrical ; the aper- 

 ture only about half as long as the spire, thus differing 

 from L. truncatulus, which is oval, with the aperture 

 and spire about equal. 



L.2^eregerhdiS an oval shell, averaging half an inch in length, 

 having a small spire, with the body-whorl suddenly in- 

 flated, and the aperture oval and large, but the different 

 varieties of this species are very puzzling. 



L. Auricularia has a rather larger shell with pointed spire, 

 and the last whorl so inflated as to make the breadth 

 almost equal to the length ; the columellar lip is much 

 twisted. 



L. Burnettii has the spire of its oval shell almost sunk, 



while that of L, involutus is depressed lower than the 



outer edge of the last whorl. 



L. glutinosus has a light and thin shell, shaped like L. Bur- 



nettii, but with an exserted spire. 



Physa hypiorum and fontinalis. — The horns of these 



water-snails are long, not triangular, as in Limnmis, and 

 the shells are reversed ; they are shaped like those of Lim- 



