﻿4 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  YOL. 
  67 
  

  

  rounding 
  the 
  lumen 
  seems 
  to 
  be 
  a 
  constant 
  feature 
  in 
  Apiocrinus, 
  as 
  

   well 
  as 
  in 
  some 
  other 
  genera, 
  as 
  for 
  instance, 
  Prolsocrinus 
  A. 
  H. 
  

   Clark 
  7 
  a 
  Recent 
  member 
  of 
  the 
  same 
  family. 
  It 
  varies 
  from 
  

   strongly 
  marked 
  and 
  deeply 
  sunken 
  to 
  flush 
  with 
  the 
  rest 
  o'f 
  the 
  

   surface. 
  So 
  far 
  as 
  can 
  be 
  ascertained, 
  it 
  seems 
  to 
  be 
  most 
  marked 
  at 
  

   the 
  top 
  of 
  the 
  stem 
  just 
  beneath 
  the 
  conical 
  enlargement, 
  gradually 
  

   becoming 
  less 
  marked 
  and 
  finally 
  obliterated 
  below. 
  The 
  flush 
  sur- 
  

   face 
  of 
  the 
  inner 
  ring 
  resembles 
  the 
  same 
  structure 
  in 
  Apiocrinus 
  

   polycryphus, 
  as 
  shown 
  by 
  De 
  Loriol 
  on 
  plate 
  36, 
  figure 
  4&. 
  In 
  com- 
  

   paring 
  the 
  figures 
  of 
  De 
  Loriol 
  which 
  I 
  have 
  copied 
  with 
  those 
  of 
  our 
  

   species, 
  it 
  must 
  be 
  remembered 
  that 
  while 
  the 
  former 
  are 
  natural 
  

   size, 
  the 
  latter 
  are 
  one 
  and 
  a 
  half 
  times 
  enlarged. 
  

  

  If 
  we 
  had 
  the 
  calyx 
  of 
  our 
  species 
  greater 
  differences 
  might 
  be 
  

   found. 
  In 
  such 
  a 
  great 
  distance 
  migrational 
  changes 
  are 
  likely 
  to 
  

   occur. 
  On 
  the 
  other 
  hand, 
  there 
  are 
  crinoid 
  species 
  of 
  intercon- 
  

   tinental 
  distribution, 
  for 
  example 
  Pentacrimis 
  sub 
  an 
  g 
  id 
  avis, 
  one 
  of 
  

   the 
  best 
  known 
  European 
  species, 
  of 
  Jurassic 
  age, 
  which 
  has 
  been 
  

   found 
  in 
  Alaska, 
  with 
  characters 
  so 
  nearly 
  identical 
  that 
  only 
  varietal 
  

   differences, 
  if 
  any, 
  can 
  be 
  pointed 
  out. 
  And 
  even 
  among 
  existing 
  

   crinoids, 
  although 
  rarely, 
  an 
  equal 
  extension 
  of 
  range 
  may 
  be 
  found, 
  

   as 
  in 
  the 
  case 
  of 
  Rhizocrinus 
  lofotensis. 
  which 
  occurs 
  from 
  Florida 
  to 
  

   Greenland 
  and 
  eastward 
  to 
  Norway. 
  

  

  T 
  Proc. 
  U. 
  S. 
  Nat. 
  Mus..v<>1. 
  38, 
  1910. 
  p. 
  390. 
  fis. 
  ::. 
  

  

  