﻿U. 
  S 
  NATIONAL 
  MUSEUM 
  

  

  PROCEEDINGS, 
  VOL. 
  XX 
  PL. 
  LXVII 
  

  

  Crayfishes. 
  

  

  Figs. 
  1, 
  '2. 
  Cambarus 
  chapolanus. 
  Figs. 
  3, 
  4. 
  Parasiacus 
  defoi^sus. 
  

  

  For 
  explanation 
  of 
  plate 
  see 
  page 
  693. 
  

  

  