﻿U. 
  S. 
  NATIONAL 
  MUSEUM 
  

  

  PROCEEDINGS, 
  VOL. 
  XX 
  PL. 
  LXXII 
  

  

  Deep 
  Sea 
  Bivalves. 
  

  

  For 
  explanation 
  of 
  plate 
  see 
  page 
  i 
  

  

  