CLASSES, ORDERS, ETC. 69 



shallow; mouth oval-lanceolate. Length |- to |ths inch. Ponds, 

 ditches, and slow-running streams. More or less local. 



P. (Aplecta) hypnorum^ 



(b) Shell oval, thin, glossy, semi-transparent, pale greyish-horn 

 coloured ; whorls four to five, tumid, the last one occupying |ths or 

 iths of the shell ; suture deep ; mouth oblong and wider and larger 

 in proportion than in P. hypnorum. Length | inch. Running 

 brooks, canals, ditches, and sluggish rivers. Common. 



P. fontinalis 



(c) Shell an elongated ovoid, ventricose, glossy, finely striated 

 longitudinally, light homy or whitish in colour ; whorls three, 

 the last one f ths of the total height of the shell ; suture moderately 

 deep; apex sharp; mouth obliquely and narrowly oval, acute 

 above. Height ^rd to frds inch. In one of the lily tanks in 

 Kew Gardens, Imported. P. acuta. 



8. Limnaea. Shell oval, thin, translucent ; mouth oblong ; 

 columella with an oblique plait ; non-operculated. Animal with 

 two short triangular tentacles bearing the eyes at their base ; foot 

 oval. 



(a) Shell oval, globular, amber or yellowish-horn coloured, thin, 

 transparent ; whorls three to four, inflated, the last one forming 

 nearly the whole of the shell ; spire slightly produced ; suture 

 rather deep ; mouth oval. Mantle partly covering the shell. 

 Length ^ inch. Ditches, ponds, and lakes. Very local. 



L. glutinosa? 1 



(b) Shell ovate, thin, fragile, glossy, pale amber-coloured, glossy, 

 whorls three to four, convex, the body whorl very large ; spire 

 sunk within the last whorl ; suture shallow ; mouth pyriform, 

 large. Length 5^ lines. In a small alpine lake on Cromaglaun 

 Mountain, Killarney, Ireland. L. involuta. 



(c) Shell oval, last whorl swollen, thin, glossy, yellowish-horn 



29 v. cuprella, copper-coloured, whorls six, convex, the last one far exceeding 

 in size the rest put together, mouth oval, contracted above ; v. major > larger, 

 more coloured, height 10 to 13 mm; m. decollatttm, spire decollated. 



30 v. albina, milk-white ; v. oblonga, spire considerably produced ; v. injlata^ 

 larger, more ventricose ; v. curia, spire extremely short ; m. dextrorsum, spire 

 dextral. 



31 Y, mucronata, not quite so globular, spire more produced, 



