﻿THE 
  " 
  WEISSER 
  JURA 
  " 
  OF 
  BAVARIA. 
  151 
  

  

  smallest 
  basal 
  projects, 
  is, 
  oddly 
  enough, 
  the 
  next 
  in 
  depth 
  ; 
  but 
  

   the 
  suture-line 
  cannot 
  be 
  seen 
  lying 
  in 
  it. 
  The 
  groove 
  to 
  the 
  right 
  

   of 
  that 
  last 
  mentioned 
  is 
  very 
  little 
  less 
  marked, 
  but 
  that 
  to 
  the 
  left 
  

   is 
  a 
  very 
  faint 
  depression 
  ; 
  in 
  both 
  these 
  grooves, 
  however, 
  the 
  

   sutures 
  are 
  quite 
  clearly 
  seen. 
  One 
  of 
  the 
  two 
  large 
  radial 
  s 
  was 
  

   described 
  above 
  as 
  slightly 
  broader 
  than 
  the 
  other 
  ; 
  this 
  radial 
  lies 
  

   between 
  the 
  deepest 
  groove 
  and 
  the 
  shallowest 
  groove. 
  Each 
  of 
  the 
  

   two 
  large 
  radials 
  has 
  an 
  extremely 
  faint 
  median 
  longitudinal 
  de- 
  

   pression 
  ; 
  and 
  in 
  the 
  larger 
  of 
  the 
  two 
  this 
  depression 
  is 
  bounded 
  

   on 
  either 
  side 
  by 
  an 
  equally 
  faint 
  elevation. 
  

  

  Ornament 
  on 
  Eadials 
  (PI. 
  VI. 
  figs. 
  1, 
  2, 
  6). 
  — 
  On 
  the 
  surface 
  of 
  

   each 
  radial 
  the 
  naked 
  eye 
  can 
  just 
  perceive 
  a 
  series 
  of 
  fine 
  lines 
  ; 
  

   these 
  run 
  across 
  the 
  radial 
  from 
  groove 
  to 
  groove, 
  and 
  are 
  bent 
  

   down 
  in 
  the 
  middle 
  in 
  an 
  aboral 
  direction, 
  so 
  that 
  each 
  is 
  parallel 
  to 
  

   the 
  curved 
  lower 
  end 
  of 
  the 
  radial 
  ; 
  as 
  seen 
  with 
  unaided 
  vision 
  or 
  

   under 
  a 
  weak 
  lens, 
  this 
  gives 
  the 
  radial 
  an 
  imbricated 
  appearance. 
  

   Seen 
  under 
  a 
  higher 
  power 
  the 
  apparent 
  imbrication 
  vanishes, 
  the 
  

   lines 
  are 
  not 
  so 
  regular, 
  and 
  have 
  a 
  tendency 
  to 
  run 
  in 
  sets, 
  the 
  

   lines 
  in 
  each 
  set 
  occasionally 
  anastomosing 
  ; 
  it 
  was 
  this 
  arrangement 
  

   in 
  sets 
  that 
  looked 
  like 
  imbrication 
  to 
  the 
  naked 
  eye. 
  A 
  still 
  

   higher 
  power 
  shows 
  that 
  the 
  lines 
  are 
  produced 
  by 
  the 
  concurrence 
  

   of 
  minute 
  granules 
  similar 
  to 
  those 
  observed 
  on 
  the 
  basals 
  (PI. 
  VI. 
  

   fig. 
  6) 
  ; 
  the 
  arrangement 
  is 
  not 
  unlike 
  the 
  curved 
  lines 
  produced 
  in 
  

   iron 
  filings 
  by 
  the 
  approach 
  of 
  a 
  magnet. 
  The 
  great 
  resemblance 
  

   of 
  this 
  ornamentation 
  to 
  the 
  lines 
  of 
  growth 
  in 
  many 
  species 
  of 
  

   Serpula, 
  notably 
  S. 
  vertebralis 
  and 
  S. 
  tetragona, 
  the 
  contemporaries 
  

   of 
  our 
  crinoid, 
  combined 
  with 
  other 
  points 
  of 
  superficial 
  resemblance 
  

   to 
  the 
  fragments 
  of 
  those 
  fossils, 
  is 
  very 
  deceptive 
  ; 
  but 
  whereas 
  the 
  

   ornament 
  of 
  Serpula 
  is 
  a 
  true 
  imbrication, 
  and 
  is 
  increased 
  by 
  

   weathering, 
  the 
  lines 
  on 
  this 
  crinoid 
  are 
  merely 
  superficial 
  and 
  are 
  

   destroyed 
  by 
  attrition. 
  

  

  The 
  Spines 
  of 
  the 
  Badials. 
  — 
  Each 
  of 
  the 
  radials 
  is 
  prolonged 
  at 
  

   its 
  right 
  upper 
  corner 
  into 
  a 
  process 
  ; 
  in 
  the 
  present 
  specimen 
  only 
  

   one 
  of 
  these 
  is 
  completely 
  preserved, 
  that, 
  namely, 
  belonging 
  to 
  the 
  

   right 
  of 
  the 
  two 
  smaller 
  radials 
  (PL 
  VI. 
  fig. 
  2). 
  The 
  section 
  of 
  

   this 
  process 
  is 
  an 
  acute-angled 
  isosceles 
  triangle, 
  with 
  the 
  base 
  of 
  

   the 
  triangle 
  facing 
  inwards 
  (PL 
  VI. 
  fig. 
  3). 
  The 
  process 
  tapers 
  to 
  

   a 
  point. 
  Its 
  length 
  is, 
  from 
  the 
  point 
  whence 
  it 
  springs 
  on 
  the 
  

   suture-line 
  to 
  its 
  extremity, 
  2-5 
  mm. 
  ; 
  and 
  from 
  the 
  upper 
  surface 
  of 
  

   the 
  radial 
  to 
  its 
  extremity, 
  1*6 
  mm. 
  Each 
  of 
  the 
  two 
  larger 
  radials 
  

   possessed 
  a 
  similar 
  process 
  ; 
  but 
  that 
  of 
  one 
  is 
  broken 
  off 
  halfway 
  

   up, 
  while 
  that 
  of 
  the 
  other 
  is 
  broken 
  off 
  at 
  its 
  base. 
  The 
  left 
  of 
  

   the 
  two 
  smaller 
  radials 
  possessed 
  only 
  a 
  very 
  small 
  process 
  in 
  the 
  

   same 
  position, 
  which 
  is 
  just 
  visible 
  to 
  the 
  naked 
  eye 
  (PL 
  VI. 
  fig. 
  2). 
  

   Similarly 
  each 
  of 
  the 
  radials 
  is 
  prolonged 
  at 
  its 
  left 
  upper 
  corner 
  

   into 
  a 
  process. 
  The 
  relative 
  size 
  of 
  this 
  process, 
  as 
  compared 
  with 
  

   the 
  apposed 
  right-hand 
  process 
  of 
  the 
  next 
  radial 
  on 
  the 
  left, 
  is 
  

   variable 
  ; 
  it 
  appears 
  usually 
  to 
  have 
  been 
  shorter. 
  In 
  the 
  case 
  of 
  

   the 
  left-hand 
  larger 
  radial, 
  this 
  process 
  is 
  connected 
  with 
  the 
  process 
  

   of 
  the 
  right-hand 
  smaller 
  radial 
  mentioned 
  above 
  as 
  being 
  the 
  only 
  

  

  