﻿AIIT 
  9 
  

  

  UNUSUAL 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  

  

  59 
  

  

  sals 
  divided 
  and 
  the 
  column 
  facet 
  or 
  distinct 
  traces 
  of 
  it 
  present, 
  and 
  

   9 
  have 
  the 
  infrabasals 
  fused. 
  Taking 
  the 
  means 
  for 
  the 
  two 
  sets, 
  I 
  

   obtained 
  a 
  composite 
  for 
  each, 
  and 
  for 
  the 
  whole, 
  as 
  follows 
  : 
  

  

  Four 
  specimens 
  not 
  included 
  in 
  the 
  table, 
  while 
  having 
  the 
  same 
  

   relative 
  widths 
  otherwise, 
  have 
  the 
  anterior 
  radial 
  as 
  wide 
  as, 
  or 
  

   wider 
  than, 
  the 
  two 
  lateral 
  radials; 
  which 
  indicates 
  that 
  in 
  some 
  

   specimens 
  the 
  enlargement 
  extended 
  to 
  the 
  anterior 
  ray 
  while 
  the 
  

   two 
  posterior 
  remained 
  small, 
  which 
  might 
  not 
  be 
  unexpected 
  with 
  

   .an 
  abnormal 
  character 
  like 
  this. 
  

  

  Thus 
  it 
  appears 
  that 
  throughout 
  the 
  entire 
  assemblage 
  of 
  speci- 
  

   mens, 
  which 
  includes 
  representatives 
  of 
  the 
  best 
  known 
  species, 
  

   including 
  some 
  types, 
  the 
  radials 
  differ 
  in 
  width 
  with 
  a 
  certain 
  

   regularity 
  which 
  is 
  expressed 
  by 
  the 
  mean 
  of 
  all 
  the 
  measurements; 
  

   and 
  that 
  taking 
  this 
  mean 
  as 
  conclusive 
  evidence 
  of 
  the 
  facts, 
  the 
  

   two 
  lateral 
  radials 
  exceed 
  the 
  two 
  posterior 
  radials 
  in 
  width 
  by 
  about 
  

   1.3 
  mm., 
  and 
  the 
  anterior 
  radial 
  by 
  about 
  two 
  thirds 
  of 
  that 
  

   amount 
  — 
  this 
  excess 
  being 
  enough 
  in 
  most 
  cases 
  to 
  accommodate 
  the 
  

   greater 
  width 
  of 
  arm 
  on 
  one 
  face 
  of 
  the 
  axillary 
  primibrach, 
  the 
  faces 
  

   of 
  which 
  differ 
  in 
  the 
  proposition 
  of 
  about 
  3 
  to 
  2, 
  or 
  5 
  to 
  3. 
  Also 
  

   that 
  this 
  difference 
  is 
  not 
  confined 
  to 
  those 
  forms 
  having 
  divided 
  

   infrabasals 
  and 
  a 
  stem, 
  but 
  is 
  equally 
  pronounced 
  in 
  those 
  having 
  the 
  

   infrabasals 
  anchylosed 
  and 
  all 
  traces 
  of 
  stem 
  obliterated. 
  

  

  Among 
  the 
  material 
  under 
  consideration 
  are 
  the 
  type 
  specimens 
  

   •of 
  two 
  of 
  the 
  earliest 
  described 
  species 
  of 
  Agassizocrinus 
  : 
  1. 
  That 
  of 
  

   the 
  genotype, 
  A. 
  conicus 
  of 
  Owen 
  and 
  Shumard, 
  U. 
  S. 
  National 
  

   Museum, 
  Catalogue 
  No. 
  17937, 
  sent 
  in 
  1887 
  from 
  the 
  University 
  of 
  

   Indiana, 
  where 
  it 
  had 
  been 
  deposited 
  by 
  David 
  Dale 
  Owen, 
  along 
  

   with 
  other 
  types 
  of 
  species 
  described 
  by 
  him 
  and 
  Shumard 
  in 
  the 
  

   second 
  of 
  their 
  papers 
  in 
  the 
  Philadelphia 
  Academy 
  of 
  1852 
  (those 
  

   of 
  the 
  first 
  paper 
  being 
  now 
  in 
  the 
  University 
  of 
  Chicago) 
  ; 
  one 
  

   radial 
  is 
  not 
  visible 
  (pi. 
  15, 
  fig. 
  1). 
  2. 
  That 
  of 
  Roemer's 
  A. 
  laevis, 
  

   already 
  mentioned. 
  Corresponding 
  measurements 
  of 
  these 
  give 
  

   the 
  following 
  widths: 
  

  

  