﻿40 
  SANTA 
  MAK1A 
  OIL 
  DISTRICT, 
  CALIFORNIA. 
  

  

  this 
  shale 
  is 
  made 
  of 
  diatom 
  skeletons. 
  * 
  * 
  * 
  Even 
  when 
  the 
  

   rocks 
  are 
  flinty 
  they 
  often 
  contain 
  good 
  impressions 
  of 
  Foraminifera." 
  

   Foraminifera 
  occur 
  in 
  the 
  partially 
  ealeareous 
  shales 
  of 
  the 
  Santa 
  

   Maria 
  district, 
  and 
  in 
  places 
  the 
  limestone 
  is 
  full 
  of 
  them. 
  In 
  some 
  

   specimens 
  they 
  are 
  perfectly 
  preserved 
  and 
  various 
  kinds 
  may 
  be 
  

   easily 
  seen 
  with 
  the 
  unaided 
  eye. 
  In 
  other 
  places 
  the 
  limestone 
  

   shows 
  no 
  trace 
  of 
  organisms; 
  but 
  it 
  is 
  the 
  opinion 
  of 
  the 
  writers 
  that 
  

   they 
  have 
  been 
  present 
  in 
  such 
  places 
  and 
  have 
  lost 
  their 
  shape, 
  and 
  

   that 
  foraminiferal 
  skeletons 
  account 
  for 
  a 
  large 
  part 
  of 
  all 
  the 
  Mon- 
  

   terey 
  limestone 
  and 
  for 
  the 
  calcareous 
  portion 
  of 
  the 
  limy 
  shales. 
  

   EL 
  W. 
  Fairbanks 
  says 
  in 
  his 
  paper 
  quoted 
  on 
  page 
  — 
  that 
  the 
  lime- 
  

   stone 
  of 
  the 
  Point 
  Sal 
  region 
  " 
  appears 
  to 
  be 
  formed 
  almost 
  exclu- 
  

   sively 
  of 
  minute 
  organisms." 
  

  

  Specimens 
  representing 
  different 
  varieties 
  of 
  the 
  Monterey 
  shale 
  

   and 
  flint 
  were 
  sent 
  to 
  F. 
  J. 
  Keeley, 
  of 
  the 
  Philadelphia 
  Academy 
  of 
  

   Natural 
  Sciences, 
  who 
  very 
  kindly 
  made 
  examinations 
  of 
  them 
  and 
  

   reported 
  regarding 
  their 
  diatom 
  contents. 
  (See 
  Pis. 
  XIX 
  and 
  XX.) 
  

   He 
  found 
  diatoms 
  plentiful 
  in 
  the 
  unaltered 
  earthy 
  shale 
  and 
  less 
  com- 
  

   mon 
  in 
  the 
  more 
  compact 
  shale 
  and 
  in 
  the 
  less 
  pure, 
  either 
  gritty 
  or 
  

   argillaceous 
  shale. 
  Sponge 
  spicules 
  were 
  common 
  in 
  all 
  the 
  samples, 
  

   and 
  in 
  those 
  last 
  mentioned 
  they 
  were 
  more 
  abundant 
  than 
  diatoms. 
  

   No 
  examination 
  was 
  made 
  of 
  the 
  indurated 
  varieties. 
  Mr. 
  Keeley 
  

   was 
  unable 
  to 
  make 
  more 
  than 
  a 
  hasty 
  examination, 
  but 
  on 
  request 
  

   he 
  estimated 
  roughly 
  that 
  the 
  purest 
  material 
  contained 
  from 
  5 
  to 
  10 
  

   per 
  cent 
  of 
  diatoms 
  and 
  that 
  the 
  soft 
  shale 
  in 
  which 
  fewer 
  could 
  be 
  

   seen 
  contained 
  possibly 
  1 
  per 
  cent. 
  He 
  found 
  a 
  few 
  Radiolaria 
  but 
  

   no 
  Foraminifera 
  in 
  the 
  pure 
  siliceous 
  shale, 
  diatoms 
  and 
  next 
  to 
  them 
  

   sponge 
  spicules 
  being 
  by 
  far 
  the 
  predominant 
  organic 
  remains. 
  

  

  C. 
  S. 
  Boyer, 
  of 
  the 
  Philadelphia 
  Academy 
  of 
  Natural 
  Sciences, 
  kindly 
  

   identified 
  the 
  species 
  of 
  diatoms 
  in 
  two 
  slides 
  prepared 
  by 
  Mr. 
  Keeley 
  

   from 
  the 
  two 
  purest 
  samples 
  of 
  diatomaceous 
  earth 
  that 
  were 
  sent 
  to 
  

   him. 
  Mr. 
  Keeley 
  says: 
  "The 
  lists 
  made 
  by 
  Mr. 
  Boyer 
  cover 
  only 
  

   the 
  species 
  he 
  saw 
  in 
  the 
  slides 
  sent 
  him, 
  and 
  an 
  exhaustive 
  examina- 
  

   tion 
  of 
  the 
  material, 
  which 
  would 
  require 
  searching 
  over, 
  say, 
  a 
  hun- 
  

   dred 
  slides 
  or 
  more, 
  would 
  probably 
  give 
  a 
  long 
  list 
  of 
  species, 
  many 
  

   of 
  which 
  might 
  not 
  be 
  seen 
  more 
  than 
  once 
  or 
  twice 
  in 
  the 
  course 
  of 
  

   such 
  an 
  examination." 
  Nevertheless, 
  these 
  lists 
  probably 
  indicate 
  

   the 
  commonest 
  species. 
  In 
  the 
  slide 
  made 
  from 
  the 
  shale 
  at 
  the 
  base 
  

   of 
  the 
  Monterey 
  from 
  the 
  locality 
  above 
  referred 
  to 
  at 
  the 
  junction 
  

   of 
  Salsipuedes 
  and 
  El 
  Jaro 
  creeks 
  Mr. 
  Boyer 
  found 
  the 
  following 
  

   diatoms 
  : 
  

  

  Coseinodiscus 
  marginatum 
  Ehrenberg. 
  

   Coscinodiscufl 
  marginatus 
  var. 
  intermedia 
  Rattray. 
  

  

  Coseinodiscus 
  robustus 
  Grow 
  

   Ajachnodiscus 
  i 
  fragment 
  I. 
  

   Diploneis? 
  (fragment 
  I. 
  

   Melosira 
  sulcata 
  Ehrenberg 
  (rare). 
  

  

  