﻿276 
  

  

  G. 
  B. 
  Wieland 
  — 
  On 
  Liassic 
  Floras. 
  

  

  Bearing 
  in 
  mind, 
  now, 
  that 
  it 
  is 
  not 
  the 
  new 
  species 
  of 
  a 
  

   more 
  or 
  less 
  cosmopolitan 
  early 
  to 
  mid-Mesozoic 
  flora, 
  however 
  

   broadly 
  identified, 
  but 
  the 
  old 
  and 
  better 
  known 
  elements 
  that 
  

   must 
  in 
  the 
  primary 
  instance 
  afford 
  a 
  basis 
  of 
  comparison, 
  it 
  is 
  

   well 
  to 
  take 
  both 
  the 
  trouble 
  and 
  the 
  space 
  to 
  give 
  the 
  age 
  

   usually 
  assigned 
  to 
  the 
  better 
  known 
  elements 
  recurring 
  in 
  the 
  

   Mixteca 
  Alta 
  flora 
  in 
  a 
  further 
  subjoined 
  table, 
  Yla. 
  

  

  Table 
  Via. 
  — 
  Assigned 
  Age 
  of 
  Oaxacan 
  Plants. 
  

  

  Ehatic 
  (or 
  Triassic) 
  

  

  Liassic 
  

  

  Oolitic 
  

  

  Zamites 
  Holkeri 
  

  

  " 
  confusus 
  

  

  Pterophyllum 
  of. 
  

  

  contiguum 
  

  

  Ptilophyllums 
  

   Otozarnites 
  obtusus 
  

  

  " 
  Molinianus 
  

   " 
  Mandelslohi 
  

  

  Ptilophyllums 
  

   Otozarnites 
  ( 
  Williamsonia) 
  

   Williamsonia 
  (fruit 
  species) 
  

   Yuccites 
  

  

  Laccopteris 
  (?) 
  

   Nceggerath 
  iopsis 
  

   Alethopteris 
  

   Glossopteris 
  

  

  " 
  Reg 
  lei 
  

   " 
  Juarezii 
  

   Pterozamites 
  (Ptero- 
  

   phyllum) 
  

   Pterophyllum 
  (mini- 
  

   ster 
  i) 
  

   Ano?nozamites 
  Lind- 
  

  

  

  

  

  

  leyanus 
  

   Cycadolepis 
  

   Phoenicopsis 
  

   Stangerites 
  

   Sagenopteris 
  

  

  (Rhat 
  to 
  Lias) 
  

  

  

  It 
  is 
  here 
  seen 
  that 
  when 
  keeping 
  in 
  mind 
  the 
  specimens 
  

   themselves, 
  as 
  well 
  as 
  lists, 
  about 
  eight 
  of 
  the 
  old 
  elements 
  are 
  

   upper 
  Triassic 
  or 
  Rhatic, 
  and 
  only 
  four 
  are 
  of 
  somewhat 
  

   Inferior 
  Oolite 
  stamp, 
  while 
  the 
  great 
  bulk 
  of 
  the 
  forms 
  are 
  

   "Liassic." 
  It 
  is, 
  therefore, 
  found 
  that 
  the 
  plant 
  beds 
  of 
  the 
  

   El 
  Consuelo 
  section 
  begin 
  at 
  the 
  upper 
  borders 
  of 
  the 
  Rhatic 
  

   and 
  probably 
  extend 
  through 
  the 
  Liassic 
  near 
  to 
  the 
  lowermost 
  

   Inferior 
  Oolite. 
  

  

  And 
  in 
  so 
  far 
  as 
  the 
  position 
  of 
  the 
  plant 
  beds 
  is 
  open 
  to 
  dis- 
  

   pute 
  and 
  adjudication 
  following 
  the 
  critical 
  study 
  of 
  the 
  inver- 
  

   tebrates 
  of 
  the 
  great 
  series 
  of 
  superposed 
  marine 
  deposits 
  in 
  

   the 
  El 
  Consuelo 
  Section, 
  I 
  would 
  first 
  yield 
  by 
  classing 
  the 
  

   plant 
  beds 
  still 
  more 
  simply 
  as 
  youngest 
  Jurassic. 
  The 
  flora, 
  

   as 
  already 
  explained, 
  appears 
  to 
  have 
  been 
  but 
  briefly 
  estab- 
  

   lished 
  rather 
  than 
  old, 
  a 
  fact 
  quite 
  in 
  accordance 
  with 
  the 
  

   sequence 
  of 
  geologic 
  events 
  leading 
  up 
  to 
  the 
  deposition 
  of 
  

   the 
  plant 
  beds. 
  

  

  