﻿GEOL. 
  SOC. 
  AM., 
  MEMOIR 
  76 
  

  

  PALMER, 
  PL. 
  33 
  

  

  

  

  ISCHNOCHITON, 
  MOPALIA, 
  BASILIOCIIITON. 
  AND 
  CALLISTOCHJTON 
  

  

  