﻿330 
  Verrill 
  — 
  Notes 
  on 
  the 
  Geology 
  of 
  the 
  Bermudas. 
  

  

  together 
  with 
  a 
  few 
  small 
  fragments 
  of 
  seolian 
  limestone 
  and 
  

   particles 
  of 
  coal 
  and 
  cinders 
  from 
  steamers. 
  

  

  The 
  shells, 
  on 
  the 
  average, 
  constitute 
  about 
  80 
  to 
  90 
  per 
  

   cent 
  of 
  the 
  whole 
  mass 
  ; 
  limestone 
  detritus 
  perhaps 
  5 
  per 
  cent. 
  

  

  The 
  shells 
  are 
  mostly 
  recently 
  dead. 
  Their 
  generally 
  broken 
  

   condition 
  (fig. 
  9) 
  is 
  due 
  to 
  the 
  fact 
  that 
  they 
  have 
  mostly 
  been 
  

   swallowed 
  and 
  passed 
  through 
  the 
  intestines 
  of 
  the 
  large 
  sea- 
  

   urchins 
  (Toxopneustes), 
  and 
  two 
  species 
  of 
  large 
  holothurians 
  

   (Stichopus), 
  which 
  are 
  very 
  abundant 
  everywhere 
  on 
  these 
  

   sandy 
  bottoms, 
  and 
  whose 
  large 
  intestines 
  are 
  always 
  found 
  

  

  Figure 
  8. 
  — 
  Sample 
  of 
  shell-sand 
  from 
  off 
  Bailey 
  Bay 
  in 
  4 
  fathoms, 
  x 
  1-^. 
  

   Figure 
  9. 
  — 
  Shell-sand 
  from 
  main 
  Ship 
  Channel, 
  in 
  6 
  fathoms, 
  x 
  1|. 
  

  

  filled 
  with 
  the 
  sand. 
  Many 
  of 
  the 
  abundant 
  smaller 
  fishes 
  

   also 
  feed 
  largely 
  on 
  the 
  shells, 
  as 
  do 
  some 
  of 
  the 
  crabs. 
  All 
  

   these 
  creatures, 
  and 
  others, 
  are 
  in 
  fact 
  continually 
  at 
  work 
  kill- 
  

   ing 
  and 
  breaking 
  up 
  the 
  shells, 
  large 
  and 
  small. 
  Such 
  mol- 
  

   lusks 
  are, 
  however, 
  very 
  prolific 
  and 
  mature 
  rapidly, 
  so 
  that 
  

   they 
  are 
  able 
  to 
  keep 
  up 
  their 
  customary 
  numbers. 
  

  

  Subwrial 
  Erosion. 
  

   In 
  the 
  Bermudas, 
  owing 
  to 
  the 
  equable 
  climate 
  and 
  absence 
  

   of 
  frost, 
  the 
  phenomena 
  of 
  erosion 
  and 
  subserial 
  disintegration 
  

   of 
  the 
  rock 
  is 
  very 
  much 
  simplified, 
  as 
  compared 
  with 
  Europe 
  

   and 
  the 
  greater 
  part 
  of 
  North 
  America. 
  There 
  is 
  every 
  

   reason 
  for 
  believing 
  that 
  the 
  present 
  conditions 
  have 
  continued 
  

   for 
  an 
  immense 
  period 
  of 
  time, 
  without 
  much 
  change 
  in 
  this 
  

   respect. 
  Therefore 
  observations 
  that 
  would 
  give 
  a 
  fairly 
  accu- 
  

   rate 
  measure 
  of 
  the 
  present 
  average 
  rate 
  of 
  disintegration 
  of 
  

   the 
  limestone 
  would 
  be 
  of 
  great 
  value 
  in 
  determining 
  the 
  time 
  

   required 
  for 
  the 
  great 
  changes 
  that 
  have 
  taken 
  place 
  in 
  past 
  

   time. 
  So, 
  likewise, 
  we 
  might, 
  by 
  a 
  careful 
  study 
  of 
  the 
  forma- 
  

  

  