﻿Kindle 
  — 
  Factor 
  in 
  Rounding 
  of 
  Sand 
  Grains. 
  433 
  

  

  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 
  filled 
  with 
  

   the 
  sand. 
  Many 
  of 
  the 
  abundant 
  smaller 
  fishes 
  also 
  feed 
  

   largely 
  on 
  the 
  shells, 
  are 
  in 
  fact 
  continually 
  at 
  work 
  kill- 
  

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

   mollusks 
  are 
  however 
  very 
  prolific 
  and 
  mature 
  rapidly 
  so 
  

   that 
  they 
  are 
  able 
  to 
  keep 
  up 
  their 
  customary 
  numbers. 
  ' 
  ' 
  

  

  Henderson 
  7 
  gives 
  the 
  following 
  observations 
  on 
  the 
  

   feeding 
  habits 
  of 
  sea-urchins 
  and 
  holothurians 
  in 
  Cuban 
  

   waters 
  : 
  

  

  " 
  Owing 
  to 
  the 
  shifting 
  nature 
  of 
  the 
  sands 
  the 
  flats 
  

   seemed 
  to 
  be 
  very 
  bare 
  of 
  life 
  excepting 
  for 
  the 
  many 
  

   white-spined 
  sea-urchins, 
  some 
  large 
  stars, 
  and 
  a 
  few 
  

   holothurians. 
  All 
  of 
  these 
  creatures, 
  especially 
  the 
  lat- 
  

   ter, 
  were 
  busily 
  at 
  work 
  triturating 
  the 
  coarse 
  organic 
  

   matter 
  it 
  contains 
  subjecting 
  it 
  to 
  a 
  grinding 
  process. 
  

   The 
  amount 
  of 
  coarse 
  sand 
  thus 
  quickly 
  reduced 
  to 
  finer 
  

   particles 
  is 
  far 
  greater 
  than 
  one 
  would 
  at 
  first 
  suppose. 
  

   No 
  doubt 
  the 
  feeding 
  habits 
  of 
  these 
  echinoderms 
  con- 
  

   stitute 
  an 
  important 
  factor 
  in 
  the 
  breaking 
  down 
  process 
  

   of 
  reef 
  from 
  massive 
  rock 
  to 
  fine 
  mud." 
  

  

  Various 
  other 
  naturalists, 
  among 
  them 
  Sharpey 
  8 
  and 
  

   Butler, 
  9 
  have 
  noted 
  the 
  sand-eating 
  habits 
  of 
  sea-urchins. 
  

  

  Sea-urchins 
  occur 
  in 
  abundance 
  wherever 
  conditions 
  

   are 
  favorable 
  to 
  their 
  existence. 
  On 
  the 
  shores 
  of 
  Grand 
  

   Manan 
  island 
  in 
  the 
  Bay 
  of 
  Fundy 
  Dr. 
  Wm. 
  Simpson 
  

   found 
  "such 
  numbers 
  of 
  sea-urchins 
  that 
  it 
  is 
  impossible 
  

   to 
  make 
  a 
  step 
  without 
  crushing 
  one 
  or 
  more 
  of 
  them. 
  " 
  10 
  

   Verrill 
  reports 
  sea-urchins 
  as 
  "very 
  abundant 
  in 
  the 
  Bay 
  

   of 
  Fundy 
  from 
  low 
  water 
  to 
  109 
  fathoms." 
  11 
  Scott 
  

   reports 
  sea-urchins 
  so 
  abundant 
  at 
  some 
  localities 
  in 
  the 
  

   Bay 
  of 
  Fundy 
  that 
  "they 
  are 
  massed 
  in 
  heaps, 
  often 
  

   obscuring 
  the 
  bottom." 
  12 
  

  

  7 
  Henderson, 
  J. 
  B. 
  : 
  The 
  Cruise 
  of 
  the 
  Tomas 
  Barrera, 
  pp. 
  131-132, 
  1916. 
  

  

  8 
  Sharpey, 
  W. 
  : 
  Echinodermata, 
  Todd 
  's 
  Cyclopaedia 
  of 
  Anatomy 
  and 
  

   Physiology, 
  vol. 
  2, 
  p. 
  39, 
  London, 
  1838. 
  

  

  9 
  Butler, 
  F. 
  H. 
  : 
  Echinodermata. 
  Encyclopaedia 
  Britannica, 
  ninth 
  edition, 
  

   vol. 
  7, 
  p. 
  631, 
  Edinburgh, 
  1877. 
  

  

  10 
  Stimpson, 
  W. 
  : 
  Proceedings 
  of 
  the 
  Boston 
  Soc. 
  Nat. 
  Hist., 
  vol. 
  4, 
  p. 
  

   96, 
  1854. 
  

  

  "Verrill, 
  A. 
  E. 
  : 
  Eept. 
  upon 
  Invertebrate 
  Animals 
  of 
  Vineyard 
  Sound 
  

   and 
  the 
  adjacent 
  waters 
  with 
  an 
  Account 
  of 
  the 
  Physical 
  Characters 
  of 
  the 
  

   Eegion, 
  Eept. 
  Comm. 
  Pish 
  and 
  Fisheries, 
  Washington, 
  1874. 
  

  

  12 
  Scott, 
  P. 
  H.: 
  Food 
  of 
  the 
  Sea-Urchin, 
  Contr. 
  Can. 
  Biol., 
  p. 
  53, 
  1901. 
  

  

  