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 My sea 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. 

 rhomboidezis (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. 



j\fya margaritifera, Linn. Syst. Nat. ed. xii. p. 1112. JJ. margaritiferus, 

 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 : gilJs greyish-brown, with whitish 

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

 thirds of their length. 



Shell oblong, much compressed, sohd, having a dull surface, 

 dark bro^vn, or nearly black, transversely and irregularly 

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

 obscure longitudinal striae, which are interrupted by the fines 

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

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

 region not prominent, always decorticated or eroded, and to 

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

 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 : lovjer 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. 



