EXPLANATION OF PLATES 



The photographic illustrations shown on Plates 27, 28, and 29 are from nega- 

 tives prepared by Mr. J. G. Sanders and Mr. J. G. Pratt as follows : Figures 1, 

 2, 3, and 4 of Plate 27 ; Figures 1, 4, and 6 of Plate 28 ; and Figures 1, 2, 3, 4, 5, 

 and 6 of Plate 29 are from negatives made by Mr. Sanders ; Figures 5 and 6 of 

 Plate 27; and Figures 2, 3, and 5 of Plate 28 are from negatives made by Mr, 

 Pratt. 



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