﻿128 
  A. 
  E. 
  Verrill 
  — 
  Echinoderms 
  of 
  Northeastern 
  America. 
  

  

  Bathymetrical 
  Distribution 
  of 
  N. 
  E. 
  American 
  Echinoderms. 
  

  

  Fathoms. 
  Aster. 
  Opbiur. 
  Crin. 
  Echin. 
  Holoth. 
  Total. 
  

  

  0-50 
  26 
  17 
  1 
  5 
  25 
  74 
  

  

  50-100 
  37 
  20 
  2 
  12 
  12 
  83 
  

  

  100-500 
  35 
  30 
  2 
  17 
  9 
  93 
  

  

  500-1000 
  24 
  26 
  2 
  10 
  11 
  73 
  

  

  1000-2000 
  22 
  26 
  1 
  12 
  13 
  74 
  

  

  2000-2600 
  7 
  7 
  2 
  5 
  21 
  

  

  It 
  will 
  be 
  seen 
  from 
  the 
  above 
  table 
  that 
  the 
  species 
  of 
  

   Echinoderms 
  are 
  more 
  numerous 
  between 
  100 
  and 
  500 
  fathoms 
  

   than 
  in 
  any 
  other 
  zone 
  of 
  depth. 
  It 
  is 
  also 
  in 
  this 
  zone 
  that 
  

   many 
  species 
  occur 
  in 
  the 
  greatest 
  abundance 
  of 
  individuals. 
  

   This 
  is 
  largely 
  due 
  to 
  the 
  fact 
  that 
  off 
  much 
  of 
  our 
  coast, 
  a 
  

   profuse 
  fauna 
  is 
  sustained 
  at 
  those 
  depths 
  by 
  the 
  direct 
  influ- 
  

   ence 
  of 
  the 
  Gulf 
  Stream, 
  as 
  shown 
  in 
  several 
  of 
  my 
  former 
  

   articles. 
  

  

  A 
  brief 
  statement 
  of 
  some 
  of 
  the 
  results 
  and 
  conclusions, 
  

   arrived 
  at 
  from 
  the 
  study 
  of 
  this 
  group, 
  may 
  be 
  given 
  here, 
  

   leaving 
  a 
  more 
  detailed 
  discussion 
  of 
  the 
  subject 
  for 
  another 
  

   occasion. 
  

  

  1. 
  The 
  abyssal 
  genera 
  and 
  families 
  are 
  mostly 
  very 
  widely 
  

   diffused 
  over 
  the 
  three 
  great 
  ocean 
  basins. 
  

  

  2. 
  The 
  species 
  belonging 
  to 
  abyssal 
  genera 
  are 
  usually 
  re- 
  

   stricted 
  in 
  range 
  to 
  particular 
  regions 
  or 
  to 
  a 
  single 
  ocean. 
  

  

  3. 
  Those 
  genera 
  and 
  species 
  having 
  the 
  greatest 
  bathymetri- 
  

   cal 
  range 
  are 
  also 
  generally 
  the 
  most 
  widely 
  distributed 
  geo- 
  

   graphically. 
  Some 
  of 
  these 
  species 
  range 
  from 
  very 
  shallow 
  

   water 
  to 
  1000 
  fathoms 
  or 
  more, 
  and 
  may 
  extend 
  geographically 
  

   into 
  all 
  the 
  great 
  oceans. 
  

  

  4. 
  Some 
  of 
  those 
  species 
  belonging 
  to 
  the 
  intermediate 
  

   depths 
  (100 
  to 
  500 
  fath.), 
  known 
  as 
  the 
  " 
  continental 
  zone," 
  

   often 
  have 
  a 
  very 
  wide 
  geographical 
  range. 
  Many 
  of 
  them 
  

   extend 
  to 
  European 
  waters, 
  and 
  some 
  even 
  to 
  the 
  Pacific. 
  

  

  5. 
  Many 
  of 
  the 
  most 
  peculiar 
  and 
  remarkable 
  new 
  genera 
  

   belong 
  to 
  the 
  continental 
  zone, 
  or 
  even 
  between 
  50 
  and 
  200 
  

   fathoms. 
  

  

  6. 
  Many 
  peculiar 
  and 
  conspicuous 
  genera 
  and 
  several 
  re- 
  

   markable 
  families 
  are 
  nearly 
  or 
  quite 
  confined 
  to 
  the 
  abyssal 
  

   zone. 
  

  

  7. 
  Abyssal 
  genera 
  are 
  often 
  endowed 
  with 
  special 
  structures 
  

   adapted 
  to 
  the 
  peculiar 
  physical 
  and 
  biological 
  conditions 
  in 
  

   which 
  they 
  live, 
  especially 
  to 
  the 
  food 
  upon 
  which 
  they 
  feed 
  

   and 
  to 
  the 
  soft 
  mud 
  or 
  ooze 
  in 
  which 
  most 
  of 
  them 
  live 
  more 
  

   or 
  less 
  buried. 
  

  

  8. 
  The 
  abyssal 
  species 
  in 
  many 
  cases 
  appear 
  to 
  be 
  capable 
  

   only 
  of 
  very 
  slow 
  dispersion, 
  as 
  compared 
  with 
  shallow 
  water 
  

   species. 
  This 
  is, 
  at 
  least 
  in 
  many 
  cases, 
  due 
  to 
  the 
  fact 
  that 
  

  

  