﻿334 
  CONTRIBUTIONS 
  TO 
  THE 
  GEOLOGY 
  OF 
  

  

  III. 
  OP 
  THE 
  PLACE 
  IN 
  THE 
  GEOLOGICAL 
  SERIES 
  TO 
  WHICH 
  THESE 
  

  

  DEPOSITS 
  BELONG. 
  

  

  80. 
  That 
  the 
  strata 
  here 
  described, 
  and 
  the 
  deposits 
  identical 
  and 
  con- 
  

   tinuous 
  with 
  them, 
  stretching 
  extensively 
  to 
  the 
  north 
  and 
  south 
  into 
  

   the 
  adjoining 
  states, 
  are 
  referable 
  to 
  the 
  Miocene 
  period 
  of 
  the 
  Ameri- 
  

   can 
  Tertiary, 
  will 
  be 
  readily 
  admitted 
  on 
  adverting 
  to 
  the 
  well 
  marked 
  

   relations 
  of 
  their 
  organic 
  remains. 
  

  

  81. 
  A 
  careful 
  summary 
  of 
  the 
  fossils 
  derived 
  from 
  the 
  several 
  local- 
  

   ities 
  hitherto 
  examined 
  within 
  the 
  peninsula, 
  establishes 
  the 
  total 
  num- 
  

   ber 
  of 
  those 
  at 
  present 
  known 
  to 
  be 
  very 
  nearly 
  one 
  hundred. 
  Of 
  

   these 
  not 
  more 
  than 
  eighteen 
  are 
  ascertained 
  to 
  belong 
  to 
  species 
  now 
  

   living 
  ; 
  showing 
  a 
  remarkable, 
  though 
  no 
  doubt 
  accidental 
  coincidence 
  

   with 
  the 
  average 
  proportion 
  of 
  recent 
  species 
  found 
  in 
  deposits 
  of 
  the 
  

   Miocene 
  period 
  in 
  Europe. 
  

  

  Lest 
  it 
  may 
  seem 
  objectionable 
  to 
  institute 
  the 
  comparison 
  between 
  

   the 
  recent 
  and 
  the 
  extinct 
  shells 
  of 
  several 
  localities 
  taken 
  in 
  the 
  aggre- 
  

   gate, 
  the 
  ratio 
  has 
  been 
  examined 
  as 
  it 
  exists 
  in 
  some 
  of 
  the 
  localities 
  

   separately. 
  Thus 
  in 
  the 
  cliffs 
  at 
  King's 
  Mill 
  on 
  the 
  James 
  river, 
  the 
  

   whole 
  number 
  of 
  species 
  whose 
  analogies 
  are 
  at 
  present 
  satisfactorily 
  

   established, 
  is 
  about 
  seventy-four, 
  of 
  which 
  but 
  fourteen 
  are 
  of 
  the 
  pre- 
  

   sent 
  day, 
  or 
  recent. 
  The 
  per-centage 
  here 
  disclosed 
  is 
  therefore 
  about 
  

   nineteen, 
  being 
  nearly 
  the 
  same 
  with 
  that 
  above, 
  and 
  still 
  almost 
  

   identical 
  with 
  the 
  proportions 
  in 
  several 
  of 
  the 
  Miocene 
  localities 
  of 
  

   Europe. 
  

  

  32. 
  Making 
  every 
  possible 
  allowance 
  for 
  future 
  discoveries 
  bringing 
  

   to 
  light 
  as 
  recent, 
  some 
  of 
  the 
  now 
  supposed 
  extinct 
  species, 
  it 
  is 
  still 
  

   difficult 
  to 
  imagine, 
  with 
  such 
  a 
  ratio 
  as 
  we 
  have 
  at 
  present, 
  that 
  the 
  

   proportions 
  can 
  ever 
  so 
  far 
  change 
  as 
  to 
  make 
  the 
  living 
  species 
  of 
  the 
  

   deposit 
  to 
  equal 
  or 
  exceed 
  the 
  number 
  of 
  the 
  extinct 
  ; 
  a 
  condition 
  ne- 
  

   cessary 
  of 
  course 
  to 
  entitle 
  it 
  to 
  the 
  name 
  of 
  Older 
  Pliocene, 
  which 
  it 
  

   has 
  received. 
  

  

  33. 
  The 
  circumstance 
  that 
  in 
  Prince 
  George 
  county 
  the 
  Miocene 
  

   is 
  superimposed 
  directly 
  upon 
  Eocene, 
  from 
  which 
  it 
  seems 
  not 
  to 
  be 
  

   separated 
  by 
  any 
  features 
  which 
  would 
  mark 
  a 
  long 
  interval 
  attended 
  

  

  