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[Assembly 



SUPPLEMENTARY NOTE ON THE GENUS AMBONYCHIA. 



Since the preceding pages were printed, I liave been able, through 

 the kindness of Professor Safford of Tennessee, to illustrate more 

 fully the hinge-structure of Amhonychia radiata. The accompanying 

 figure 1 shows the hinge-line, the cardinal teeth t, and the lateral 

 teeth tt. On the anterior side, the margin of the shell is sinuate for 

 the passage of the byssus b. The latter character is likewise more 

 distinctly shown in figure 2, which is an anterior view of the right 

 valve. 



1 2 



James Hall. 



ERRATA. 



Page 10, note at bottom of page, for 1847, read 1857. 

 Page 14, note 4th line from bottom, for 1847, read 1857. 



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