﻿14 
  J. 
  S. 
  GABDNEE 
  DESCRIPTION 
  AND 
  

  

  tions 
  in 
  the 
  Arctic 
  regions 
  is 
  extremely 
  doubtful. 
  I 
  have 
  long 
  be- 
  

   lieved 
  most 
  of 
  them 
  to 
  be 
  Eocene 
  ; 
  and 
  this 
  view 
  is 
  held 
  by 
  Dawson, 
  

   Lesquereux, 
  Saporta, 
  Marcou, 
  and 
  others, 
  all 
  well 
  qualified 
  to 
  judge. 
  

   The 
  plant- 
  evidence 
  is 
  at 
  present 
  negative, 
  in 
  one 
  sense 
  ; 
  for 
  although 
  

   a 
  proportion 
  has, 
  apparently, 
  been 
  identified 
  by 
  Heer 
  with 
  those 
  of 
  

   the 
  Miocene 
  of 
  Switzerland, 
  the 
  true 
  age 
  of 
  part 
  of 
  which 
  is 
  itself 
  

   doubtful, 
  another 
  portion 
  is 
  identified 
  by 
  Dawson 
  and 
  Lesquereux 
  

   with 
  the 
  undoubtedly 
  Eocene, 
  or 
  even 
  older 
  Lower 
  Lignitic 
  of 
  

   America. 
  On 
  the 
  other 
  hand 
  it 
  appears 
  to 
  me 
  that 
  the 
  fact 
  of 
  

   there 
  being 
  a 
  similarity 
  in 
  these 
  floras 
  to 
  those 
  of 
  the 
  Miocene 
  is 
  

   against 
  their 
  being 
  of 
  that 
  age 
  ; 
  for 
  no 
  two 
  floras, 
  so 
  much 
  alike 
  and 
  

   assimilating 
  so 
  closely 
  to 
  those 
  of 
  the 
  present 
  day 
  could 
  have 
  grown 
  

   contemporaneously 
  in 
  such 
  widely 
  separated 
  latitudes 
  — 
  that 
  is, 
  if 
  

   they 
  grew 
  at 
  the 
  same 
  level, 
  as 
  is 
  commonly 
  assumed. 
  

  

  Apart 
  from 
  this, 
  we 
  have 
  the 
  following 
  arguments 
  in 
  favour 
  of 
  

   some 
  among 
  the 
  floras 
  described 
  being 
  of 
  Eocene 
  age: 
  — 
  (1) 
  the 
  fact 
  

   that 
  the 
  supposed 
  Miocenes 
  generally 
  rest 
  directly 
  on 
  the 
  supposed 
  

   Cretaceous 
  rocks 
  ; 
  (2) 
  the 
  absence 
  of 
  any 
  explanation 
  of 
  the 
  immense 
  

   gap 
  which 
  Heer's 
  grouping 
  implies, 
  and 
  of 
  which 
  there 
  is 
  no 
  strati- 
  

   graphical 
  evidence 
  ; 
  (3) 
  the 
  Eocene 
  climate 
  may 
  have 
  permitted 
  the 
  

   growth 
  of 
  the 
  floras, 
  and 
  that 
  of 
  the 
  Miocene 
  could 
  not 
  ; 
  (4) 
  the 
  pro- 
  

   bability 
  that 
  plants 
  must 
  have 
  existed 
  in 
  Eocene 
  times 
  in 
  the 
  area 
  

   (for 
  there 
  is 
  ample 
  evidence 
  that 
  it 
  was 
  then 
  land), 
  and 
  there 
  being 
  

   no 
  marine 
  deposits 
  of 
  Eocene 
  age 
  there 
  ; 
  (5) 
  the 
  improbability 
  that 
  

   Eocene 
  remains 
  can 
  have 
  alone 
  escaped 
  observation 
  in 
  a 
  series 
  of 
  

   apparently 
  consecutive 
  deposits 
  of 
  immense 
  extent 
  and 
  thickness, 
  

   abounding 
  in 
  plants, 
  and 
  continuous, 
  it 
  is 
  supposed, 
  from 
  the 
  Middle 
  

   Cretaceous 
  to 
  the 
  Miocene. 
  

  

  Whether 
  these 
  are 
  still 
  called 
  Cretaceous 
  or 
  Miocene, 
  it 
  is 
  certain 
  

   that 
  in 
  the 
  various 
  scattered 
  dicotyledonous 
  floras 
  of 
  Europe 
  and 
  

   America 
  we 
  have 
  a 
  great 
  sequence 
  of 
  floras, 
  each 
  linked 
  to 
  the 
  other 
  

   by 
  numerous 
  plants 
  contained 
  in 
  common, 
  which 
  there 
  is 
  the 
  utmost 
  

   difficulty 
  in 
  classifying 
  under 
  the 
  existing 
  divisions 
  of 
  Eocene 
  and 
  

   Miocene. 
  Even 
  the 
  introduction 
  of 
  a 
  Pal-eocene 
  division 
  and 
  the 
  

   recognition 
  of 
  an 
  Oligocene 
  formation 
  have 
  not 
  lessened 
  the 
  difficulty. 
  

   The 
  Oligocene 
  commences 
  in 
  England, 
  as 
  recently 
  brought 
  under 
  our 
  

   notice 
  by 
  Prof. 
  Judd, 
  at 
  the 
  base 
  of 
  the 
  Headon 
  series 
  ; 
  but 
  this 
  line, 
  

   unfortunately, 
  severs 
  in 
  two 
  a 
  flora 
  which 
  is 
  homogeneous, 
  from 
  the 
  

   base 
  of 
  the 
  Bournemouth 
  beds 
  to 
  the 
  Bembridge 
  marls, 
  and 
  separates 
  

   the 
  lower 
  and 
  most 
  important 
  part 
  from 
  the 
  congeneric 
  and 
  closely 
  

   identical 
  floras 
  of 
  Erance, 
  which 
  have 
  all 
  been 
  placed 
  in 
  the 
  Oligocene. 
  

   Again 
  the 
  Lower 
  Eocene 
  brings 
  together 
  in 
  one 
  formation 
  the 
  floras 
  

   of 
  Bromley, 
  Beading 
  and 
  Newhaven, 
  and 
  the 
  almost 
  perfectly 
  dis- 
  

   tinct 
  floras 
  of 
  Sheppey 
  and 
  Alum 
  Bay. 
  The 
  Miocene, 
  so 
  far 
  as 
  its 
  

   plant-beds 
  are 
  concerned, 
  embraces, 
  according 
  to 
  some 
  authors, 
  the 
  

   whole 
  Middle 
  Eocene 
  and 
  up 
  to 
  the 
  Pliocene, 
  while 
  opinions 
  still 
  

   diverge 
  as 
  to 
  what 
  are 
  the 
  characters 
  by 
  which 
  a 
  Cretaceous 
  dicotyle- 
  

   donous 
  flora 
  should 
  be 
  recognized. 
  

  

  The 
  existing 
  divisions 
  of 
  the 
  Tertiary 
  were 
  based, 
  as 
  we 
  all 
  know, 
  

   solely 
  upon 
  their 
  marine 
  Mollusca. 
  It 
  would 
  be 
  inconvenient 
  at 
  

  

  