EXPLANATION OF PLATES 



With much regret the author feels impelled to state that, owing to the demise of Mr 

 Philip Ast who for upward of 30 years lithographed with superior skill the plates for the 

 paleontologic reports, it became necessary to resort temporarily to less satisfactory 

 methods for the reproduction of the plates here presented. While this proceeding was 

 deemed judicious in order to avoid too long delay in publication, the finer details of 

 structure shown on the excellent original drawings have suffered seriously in this process 

 and so wide a departure from the standard quality of the work is deplored. 



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