﻿in 
  North 
  America. 
  207 
  

  

  Chonetes 
  Nova-ScoticaHall 
  (cf. 
  sarcinulatus 
  var. 
  plana 
  

  

  Schnur). 
  

   Chonetes 
  canadensis 
  Bill 
  (cf. 
  Leptoena 
  lata 
  Sow.). 
  

   Bellerophon, 
  two 
  species. 
  

   Holopea 
  sp. 
  

   Several 
  gastropods. 
  

   Avicula 
  cf. 
  textilis. 
  

  

  Lamellibranchs, 
  several 
  genera 
  and 
  species. 
  

   Orthoceras, 
  a 
  fragment. 
  

   Tentaculites. 
  

  

  Beyrichia 
  tuberculata 
  Kloden. 
  

   Plant 
  fragments. 
  

  

  Loose 
  specimens, 
  picked 
  up 
  in 
  various 
  places 
  in 
  the 
  county, 
  

   have 
  furnished 
  in 
  addition 
  to 
  the 
  above 
  : 
  

  

  Sp. 
  raricostus 
  BilL 
  

   Avicula 
  cf. 
  securiformis. 
  

  

  The 
  significance 
  of 
  the 
  correlation 
  of 
  this 
  Chapman 
  sand- 
  

   stone 
  with 
  the 
  Tilestone 
  of 
  Murchison, 
  is 
  found 
  in 
  the 
  fact 
  

   that 
  the 
  Tilestone 
  contains 
  the 
  topmost 
  fauna 
  of 
  the 
  original 
  

   Silurian 
  system 
  of 
  Murchison. 
  This 
  fauna 
  was 
  described 
  by 
  

   Sowerby 
  in 
  the 
  " 
  Silurian 
  System 
  " 
  (1839), 
  and 
  afterwards 
  the 
  

   Tilestone 
  was 
  placed 
  by 
  Murchison 
  himself 
  in 
  the 
  Silurian 
  

   (" 
  Siluria," 
  1854). 
  This 
  change 
  was 
  brought 
  about 
  by 
  the 
  

   recognition, 
  by 
  Murchison, 
  that 
  paleontological 
  evidence 
  is 
  of 
  

   greater 
  importance 
  in 
  the 
  determination 
  of 
  the 
  age 
  of 
  rocks 
  

   than 
  petrographical 
  evidence. 
  By 
  the 
  study 
  of 
  " 
  Silurian 
  

   System," 
  it 
  is 
  perfectly 
  evident 
  that 
  the 
  Silurian 
  system 
  was 
  

   intended 
  by 
  Murchison 
  to 
  include 
  all 
  the 
  fossiliferous 
  forma- 
  

   tions 
  lying 
  below 
  the 
  Old 
  Red 
  sandstone. 
  We 
  find 
  this 
  indi- 
  

   cated 
  clearly 
  on 
  pages 
  3 
  and 
  4, 
  and 
  still 
  more 
  clearly 
  expressed 
  

   on 
  page 
  7 
  of 
  the 
  Introduction 
  of 
  "The 
  Silurian 
  System," 
  

   where 
  are 
  found 
  the 
  following 
  words 
  (referring 
  to 
  the 
  name 
  

   Silurian) 
  : 
  ¥ 
  The 
  term 
  was 
  no 
  sooner 
  proposed 
  than 
  sanctioned 
  

   by 
  geologists, 
  both 
  at 
  home 
  and 
  abroad, 
  as 
  involving 
  no 
  theory, 
  

   and 
  as 
  simply 
  expressing 
  the 
  fact, 
  that 
  in 
  the 
  ' 
  Silurian 
  region 
  ' 
  

   a 
  complete 
  succession 
  of 
  fossiliferous 
  strata 
  is 
  interpolated 
  

   between 
  the 
  Old 
  Red 
  Sandstone 
  and 
  the 
  oldest 
  slaty 
  rocks" 
  

   We 
  find 
  that 
  the 
  reason 
  for 
  including 
  the 
  Tilestones 
  in 
  the 
  Old 
  

   Red 
  was 
  the 
  fact 
  that 
  the 
  soil 
  weathered 
  out 
  reddish 
  in 
  the 
  

   same 
  way 
  as 
  the 
  Old 
  Red 
  sandstone 
  did 
  where 
  it 
  was 
  typically 
  

   represented. 
  These 
  Tilestones, 
  however, 
  were 
  not 
  always 
  red 
  

   in 
  themselves; 
  but, 
  on 
  passing 
  below, 
  the 
  typical 
  Upper 
  Lud- 
  

   low 
  weathered 
  gray. 
  This 
  seems 
  to 
  have 
  been 
  the 
  prime 
  

   reason 
  in 
  the 
  mind 
  of 
  Murchison 
  for 
  classing 
  the 
  Tilestones 
  

   with 
  the 
  Old 
  Red. 
  When, 
  however, 
  the 
  first 
  edition 
  of 
  

   " 
  Siluria 
  " 
  was 
  written, 
  the 
  fact 
  that 
  the 
  species 
  of 
  this 
  fauna 
  

  

  