Mollusca of Great Britain. 391 
2. LAcusTRrs. 
Animal nigrescens.  Tentacula breviora. 
Testa oblonga, subdepressa, vertice excentrico ; fragilis, 
membranacea, concentricé substriata, nigrescens. 
Apertura oblonga. 
Long. 0.1.—Diam. 0.35. 
Ancylus lacustris. Müll. Verm.2. p. 199. Drap. Hist. 
des Moll. p. 47. t. 2. f. 25—27. 
Patella oblonga. Lightf. in Phil. Trans. 76. p. 168. 
t. 3. f. 1—5. 
lacustris. Gmel. Syst. Nat. 1. p. 3710. Mont. 
Test. Brit. p. 484. ! 
On water-plants in ditches, lakes, &c.; though rather a 
local species. It is not uncommon in Blackpill marsh near 
Swansea, mixed with the Planorbis nitidus. 
ADDITIONS AND CORRECTIONS. 
Page 324, for Cianella, read Cionella. 
Hzrix FOSCA, p. 330. 
Animal lutescenti-griseum, dorso flavescenti. Tentacula 
prelonga, flexilia. 
Since writing the above list, I have discovered this local 
; _species.i in great abundance in moist parts of Penll 
/— HELIX NITIDA, p. 339. 
The variety 8. is found not uncommonly under leaves, 
decaying Boleti, $c. in the woods at Penllergu co C MME 
(voL. xvi. SE Limnevs 
