MALACOZOA. GASTEROPODA. PULMOBRANCHIATA. Ill 



B. Limnaus truncdtulus fossdrius. Ditch Mud-Shell. 



Shell oblong, pointed, but generally abrupt by erosion, with 

 the turns moderately convex, thickish, distinctly stimulate and 

 often rugose ; the mouth oval-oblong, the inner lip expanded, 

 the umbilicus covered ; the colour yellowish-brown, frequently 

 with a tinge of reddish or purplish, of the interior yellowish- 

 brown, of the inner lip pinlt or white. 



Common in still muddy water, as in ponds and ditches. 



C. Limnaus truncdtulus minutus. Dwarf Mud-Shell. 



Shell ovato-oblong, pointed, with the turns well rounded, 

 glossy, striate ; the mouth ovate, the inner lip moderately ex- 

 panded ; the umbilicus covered ; the colour clear deep red- 

 dish-brown, of the interior similar, of the mouth pinkish. 



Occurs in clear brooks, rills, and sometimes mossy springs. 



Lymiiaea minuta. Var. Drap. Moll. Terr, et Fluv. 



To one or other of these varieties belong the following re- 

 ferences : 



Buccinum trimcatulum. Muller, Verm. Terr, et Fluv. ii. 130. 

 Helix fossaria. Mont. Test. Brit. 372. PI. 16. f. 9. PI. 16. f. 9. 

 bad. Lymnaea minuta. Lamk. Syst. vi. 2. 162. Ed. n. viii. 415. 

 Lymuaea minuta. Drap. Moll. Terr, et Fluv. 53 ; PL 3. f. 5, 

 6, 1. Lymnaea fossaria. Brown, Illustr. PL 42. f. 12, 13. 

 Limnaea fossaria. Flem. Brit. Anim. 274. Limnaeus truncatulus. 

 Gray's Turton. 240. 



There is a character by which Limnaeus palustris may 

 readily be distinguished from Limnaeus truncatulus, in all 

 their forms. In the former, the upper margin of the spiral 

 turns gradually slopes to a sulcato-crenulate edge, which 

 although thin has a slight rim, and is laid over the next turn 

 so as to form a little-impressed suture. In Limnaeus trunca- 

 tulus, the upper margin of the spiral turns curves in rather 

 abruptly, forming a deeply impressed suture, without any ap- 

 pearance of a rim or border. 



GENUS 2. PHYSA. BUBBLE-SHELL. 



Animal oval, spiral ; head with, two long, slender, 

 tapering tentacula, bearing eyes at their base internally; 

 mantle with two digitate lobes capable of being much 

 extended ; foot long, rather pointed behind. 



Shell sinistral, subglobose, oval, or oblong, delicate > 



