46 LIMN^IDjE, 



indistinct tubercles, narrow in front, and ending in a broad, blunt 

 tail, which is keeled ; jaw consisting of three pieces. 



Shell concave above, rather less so beneath, thick, nearly- 

 opaque, somewhat glossy, of a rufous or yellowish-brown colour, 

 usually paler on the lower side, with close-set curved striae in the 

 line of growth, as well as with finer spiral striae which are most 

 apparent in the upper volutions ; epidermis thinnish ; periphery 

 round, not keeled ; whorls 5-6, rounded, body whorl in breadth 

 about one-third of the shell ; suture deep ; mouth slightly 

 oblique, nearly round ; outer lip slightly reflected ; inner 

 lip continuous with the other and broadly spread over the base 

 of the penultimate whorl ; umbilicus wide but shallow. 



Inhabits slow streams, ponds, and ditches, but it is 

 local. It is very much larger than any of the other 

 British Planorbes, and is inactive and extremely irri- 

 table, pouring forth a copious stream of red-coloured 

 liquid when provoked. It crawls with a jerking sort 

 of movement, and is fond of floating on the surface of 

 the water. 



The capsules, usually two or three in number, are of 

 an oval or roundish form, and colourless, or much more 

 rarely of a pale pink colour; in each of them from twelve 

 to forty eggs are deposited, and the fry are hatched 

 after a lapse of fifteen or sixteen days. The shell of 

 this species during the early stages of its growth is 

 covered with a downy epidermis. 



Var. albina. — Shell white. Occurs in Surrey, B.C. Near 

 Henley-on-Thames, and Clevedon, Somerset (Rich). 



II. P. CONTOR'TUS,* Linn:6. Pl. IV. 



Body blackish, faintly tinged with red above, pale dirty 

 reddish-brown beneath ; tentacles very slender, not very trans- 

 parent, dirty brown, considerably diverging at their base ; foot 



* Twisted. 



