PISIDIUM. 133 



P. amnicum, Miiller. 



Not minute ; extremely inequilateral, sulcately striated ; urn- 

 bones not very blunt. 



Plate XXXVII. fig. 8, 9, and (Animal) Plate 0, fig. 8. 



Tellina amnica, Muller, Venn. Terr, et Fluv. pt. 2, p. 205. — Linn. Trans, 

 vol. viii. p. 60. — Turt. Conch. Diction, p. 168. — Dorset 

 Catalog, p. 31, pi. 7, f. 2, a.— Wood, General Conch, p. 153, 

 pi. 47, f. 6. — Dillw. Recent Shells, vol. i. p. 105. — Index 

 Testaceolog. pi. 3, Tell. f. 19. 

 „ rivalis, Maton, Linn. Trans, vol. iii. p. 44, pi. 13, f. 37, 38. — Donov. 

 Brit. Shells, vol. ii. pi. 64, f. 2. 

 Cardium amnicum, Mont. Test. Brit. p. 86. 



Cyclas palustris, Draparn. Moll. Ter. et Fluv. France, p. 131, pi. 10, f. 15, 16. 

 — Gras, Moll. T. et F. de la France, p. 73, pi. 6, f. 6. 

 „ obliqua, Lam. Anim. s. Vert, (ed Desh.) vol. vi. p. 269. — Nilsson, Moll. 

 Suecise, T. et Fl. p. 99.— Kickx, Moll. Brabant, p. 89. 

 Pisidium obliquum, Pfeiffer, Deutsch. Land und Sussw. Moll. pt. 1, p. 124, 

 pi. 5, f. 19, 20.— Brown, Illust. Conch. G. B. p. 94, pi. 

 39, f. 22.— Philippi, Moll. Sicil. vol. ii. p. 31. 

 Cyclas amnica, Turt. Dithyra Brit. p. 250, pi. 11, f. 15. — Flem. Brit. Anim. 

 p. 453.— Turt. Manual L. and F. W. Shells, p. 15, pi. 1, f. 5. 

 — Hanley, Recent Shells, vol. i. p. 89, pi. 3. f. 19. 

 Pisidium amnicum, Jenyns, Trans. Cambridge Phil. Soc. vol. iv. p. 309, pi. 

 21, f. 2. 



The outline of this species, which is by far the largest 

 of our British Pisidia, is more or less obliquely subovate 

 (often displaying 1 a disposition to become triangular) and 

 extremely inequilateral. The valves of the adult are mo- 

 derately ventricose (in the young they are much more 

 compressed) ; the profundity is chiefly manifested at the 

 subumbonal portion, their lower part being much more 

 shallow ; they are thin, fragile, glossy, semitransparent, 

 and generally more or less incrusted with ferruginous mat- 

 ter. The surface, which is concentrically traversed by rather 

 irregularly developed sulci, whose interstices often assume 

 the appearance of raised subimbricated stria?, is of an oli- 



