﻿Fig. 
  3. 
  

  

  Fig. 
  3. 
  — 
  Lower 
  Ordovician, 
  Dictyograptus 
  time. 
  

   Fig. 
  4. 
  

  

  

  ^>5pfe-C-_3^ 
  

  

  %-^~~\ 
  t^ti 
  — 
  ffiffi^ 
  f? 
  , 
  ^s^^8 
  

  

  ^^^^^^ 
  

  

  ^i; 
  J 
  y 
  ^ 
  y 
  *^3~7 
  - 
  r'tC/ 
  \/ 
  • 
  -? 
  

  

  f^v- 
  —\-_^o^^r^ 
  i 
  — 
  

  

  ^K 
  \ 
  [/I---!/ 
  / 
  Z3tr= 
  

  

  = 
  — 
  ^ 
  === 
  yj 
  *^3> 
  f 
  ~~-—~ 
  z 
  

  

  :^s||§§ 
  

  

  yf/ 
  \vf— 
  — 
  ~\— 
  ~- 
  

  

  

  - 
  _^^fe=^fe! 
  

  

  ifcSrT" 
  

  

  Fig. 
  4. 
  — 
  Middle 
  Ordovician, 
  Chasmops 
  time. 
  

  

  