﻿U. 
  S. 
  NATIONAL 
  MUSEUM 
  

  

  PROCEEDINGS, 
  VOL. 
  XX 
  PL. 
  LXVIII 
  

  

  Crayfishes. 
  

  

  Parastacns 
  saffo7-di. 
  

   For 
  explanation 
  of 
  pi 
  ate 
  see 
  page 
  694. 
  

  

  