﻿TRANSLATIONS 
  AND 
  NOTICES 
  

  

  Of 
  

  

  GEOLOGICAL 
  MEMOIRS. 
  

  

  On 
  the 
  Demarcation 
  of 
  the 
  " 
  Oligocene 
  " 
  Division 
  of 
  the 
  

   Tertiary 
  Period. 
  By 
  Prof. 
  Betrich. 
  

  

  [Ueber 
  die 
  Abgrenzung 
  der 
  Oligocanen 
  Tertiiirzeit. 
  Von 
  Herrn 
  Prof. 
  Beyrich. 
  

   Berichte 
  der 
  koniglichen 
  Akademie 
  der 
  Wissenschaften 
  zu 
  Berlin, 
  1858, 
  

   pp. 
  51—69.] 
  

  

  In 
  a 
  communication 
  made 
  by 
  Professor 
  Beyrich 
  to 
  the 
  Academy 
  of 
  

   Sciences 
  at 
  Berlin, 
  in 
  1854, 
  on 
  the 
  age 
  of 
  the 
  Tertiary 
  beds 
  of 
  Hesse*, 
  

   the 
  term 
  " 
  Oligocene 
  " 
  was 
  proposed 
  for 
  a 
  division 
  of 
  the 
  Tertiary 
  

   period, 
  to 
  which 
  belong 
  most 
  of 
  the 
  Tertiary 
  beds 
  in 
  Northern 
  Ger- 
  

   many, 
  certain 
  of 
  those 
  in 
  Central 
  Germany, 
  and 
  also 
  the 
  members 
  of 
  the 
  

   so-called 
  Mayence 
  Basin. 
  In 
  a 
  more 
  recent 
  memoir, 
  written 
  chiefly 
  

   as 
  an 
  explanation 
  of 
  a 
  geological 
  map 
  of 
  Northern 
  Germanyf 
  , 
  he 
  

   described 
  the 
  probable 
  extension 
  of 
  the 
  various 
  Tertiary 
  formations 
  of 
  

   that 
  area, 
  and 
  endeavoured 
  to 
  prove 
  their 
  connexion 
  with 
  those 
  of 
  

   like 
  age 
  in 
  other 
  districts. 
  Since 
  the 
  appearance 
  of 
  the 
  latter 
  memoir, 
  

   and 
  partly 
  simultaneously 
  with 
  it, 
  the 
  question 
  of 
  the 
  most 
  convenient 
  

   Tertiary 
  nomenclature, 
  and 
  the 
  more 
  important 
  one 
  of 
  the 
  natural 
  

   limits 
  of 
  the 
  Oligocene 
  period, 
  have 
  been 
  so 
  often 
  discussed 
  by 
  other 
  

   authors, 
  and 
  in 
  such 
  different 
  modes, 
  that 
  Professor 
  Beyrich 
  in 
  the 
  

   present 
  communication 
  has 
  endeavoured 
  to 
  give 
  a 
  general 
  and 
  critical 
  

   review 
  of 
  the 
  opinions 
  of 
  geologists 
  upon 
  these 
  subjects. 
  

  

  The 
  middle 
  term 
  of 
  the 
  Oligocene 
  series 
  includes 
  the 
  " 
  Fontaine- 
  

   bleau 
  Sands 
  " 
  — 
  the 
  youngest 
  marine 
  member 
  of 
  the 
  Paris 
  Basin, 
  — 
  

   about 
  the 
  classification 
  of 
  which 
  (whether 
  in 
  the 
  Eocene 
  or 
  the 
  

   Miocene 
  period) 
  there 
  has 
  been 
  so 
  much 
  discussion. 
  Professor 
  Beyrich 
  

   gives 
  a 
  brief 
  sketch 
  of 
  this 
  discussion, 
  and 
  of 
  the 
  investigations 
  which 
  

   led 
  to 
  the 
  adoption 
  of 
  the 
  terms 
  Eocene, 
  Miocene, 
  and 
  Pliocene, 
  pro- 
  

   posed 
  by 
  Sir 
  Charles 
  Lyell, 
  and 
  then 
  proceeds 
  to 
  show 
  that 
  more 
  re- 
  

   cently 
  this 
  discussion 
  has 
  been 
  revived, 
  and 
  has 
  acquired 
  a 
  greater 
  

   interest 
  and 
  importance, 
  in 
  consequence 
  of 
  its 
  having 
  gradually 
  become 
  

   known 
  that 
  beds 
  of 
  like 
  age, 
  containing 
  a 
  peculiar 
  and 
  rich 
  fauna, 
  

   occurred 
  very 
  extensively 
  in 
  other 
  European 
  regions 
  ; 
  and 
  while 
  it 
  

   was 
  admitted 
  on 
  all 
  hands 
  that 
  these 
  beds 
  should 
  have 
  a 
  definite 
  and 
  

   determined 
  position 
  in 
  one 
  of 
  the 
  great 
  divisions 
  of 
  the 
  Tertiary 
  period, 
  

   the 
  old 
  question 
  of 
  " 
  Eocene 
  or 
  Miocene 
  " 
  was 
  altered 
  in 
  this 
  new 
  

   dispute, 
  at 
  first 
  to 
  that 
  of 
  whether 
  all 
  these 
  beds 
  should 
  be 
  classed 
  as 
  

  

  * 
  Berichte 
  der 
  k. 
  Akad. 
  der 
  Wissenschaften 
  zu 
  Berlin, 
  1354, 
  pp. 
  640 
  et 
  seq. 
  

   t 
  "Ueber 
  den 
  Zusammenhang 
  der 
  norddeutschen 
  Tertiarbildungen, 
  &c," 
  

   Abhandl. 
  der 
  k. 
  Akad. 
  der 
  Wissensch. 
  zu 
  Berlin. 
  Aus 
  dem 
  Jahre 
  1855, 
  pp. 
  1 
  et 
  seq. 
  

   VOL. 
  XX. 
  — 
  PART 
  II. 
  C 
  

  

  