139 



Nerita fluviatilis. DrajJ. jj. 31. t. l.f. 1 — 4. 

 Brard, p. 194. t. 7./. 9, 10, 12. 



Alont. p. 470. Turt. Diet. 127. 



Theodoxus Lutetianus. De Montfort, ii. p. 351. 



Shell about three eighths of an inch long, and two 

 broad, convex above and flat underneath, obscurely 

 striate transversely, of a greenish or whitish colour, 

 variously checquered with spots or bands of white, 

 brown, purple or pink : spire consisting of three 

 volutions, the first very large oblong and oblique, 

 the others small and lateral : aperture horizontal, 

 semielliptic, with the margin sharp and entire ; 

 pillar white, transverse, sloping down to a sharp 

 edge, and quite entire : operculum semilunar, 

 yellowish with an orange border, and underneath 

 is a strong raised grooved spine at one end. The 

 shell is often covered with foul incrustations. 



In slow rivers adherinsc to stones. 



