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 Boss- 

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

 not at all agree with the description or figure given 

 by Turton of liis 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 littoralis), 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. 



Mt/a margaritifera, Linn. Syst. Nat. ed. xii. p. 1112. U.margariti ferns, 

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



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 surface, 

 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 Hnes 

 of growth : epidermis thick : beahs incurved, and j^laced at a 

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

 region not prominent, always decorticated or eroded, and to 

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

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

 anterior side : Jiinge-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 : lovjer tnargin 

 straight : inside pearly- Avhite, 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 : hinrje 



* Pearl -bearer. 



