Bull U. S. F. C. 1 893. Pearls and Pearl Shells. 



Plate 41. 



X 



* 



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FRESH WATER MUSSEL, Hargaritana margarUifera, SHOWING PEARL INCLUDED BETWEEN MANTLE AND SHELL. 



IN THE LOWER RIGHT-HAND CORNER. 



Specimen prepared by V. Fric, of Prague. From Botova River, Bohemia. 



