UNIO. 37 



Great Britain. A specimen named Unio Batavus in 

 Dr. Turton's collection of British shells is clearly a dwarf 

 variety of that species, and is the Unio nana of Lamarck, 

 U. amnicus of Ziegler, U. Batavus var. e. pusillus of Ross- 

 massler, and U. nanus of Dupuy. This specimen does 

 not at all agree with the description or figure given 

 by Turton of his Mysca Batava in his ' Manual ' ; and it 

 was not accompanied by any note of the locality. I do 

 not, however, despair of this species, as well as of U. 

 rhomboideus (or UttoraMs), being discovered in this 

 country. Both of them inhabit the North of France ; 

 and the latter once lived in our eastern counties. 



3. U. MARGARI'TIFER*, Linne". 



My a margaritifera, Linn. Syst. Nat. ed. xii. p. 1112. U. margariti- 

 ferus, F. & H. ii. p. 146, pi. xxxviii (as Alasmodonta margaritifera). 



BODY dirty grey, with sometimes a tint of flesh-colour ; 

 mantle bordered below with brown, and above with white ; 

 cirri oblong and dark brown -.foot large, tongue-shaped, grey- 

 ish-yellow, or dirty red : gills greyish-brown, with whitish 

 streaks : labial palps broader than long, and united for two- 

 thirds of their length. 



SHELL oblong, much compressed, solid, having a dull surf ace, 

 dark brown, or nearly black, transversely and irregularly 

 wrinkled, especially on the posterior side, with very fine but 

 obscure longitudinal striae, which are interrupted by the lines 

 of growth : epidermis thick : beaks incurved, and placed at a 

 distance of about one-fourth from the anterior side : umbonal 

 region not prominent, always decorticated or eroded, and to 

 such an extent as to expose several of the inner layers : lunule 

 narrow and indistinct : ligament very long, and extending to the 

 anterior side : hinge-line curved : anterior side rounded : pos- 

 terior side very gradually sloping and rounded at its extremity, 

 pinched-up above into a blunt keel or ridge : lower margin 

 straight: inside pearly- white, with a tint of flesh-colour and 

 blotches of olive-green in the region of the adductor muscles, 

 pitted in the middle by tubercular folds of the mantle : hinge 

 * Pearl -bearer. 



