﻿THE 
  " 
  WEISSER 
  JTJKA 
  OF 
  BAVAEIA. 
  

  

  165 
  

  

  by 
  a 
  4-rayed 
  Eug. 
  nutans. 
  The 
  present 
  species 
  has 
  reached 
  a 
  stage 
  

   (IV) 
  in 
  which 
  the 
  basals 
  are 
  fused 
  into 
  a 
  basal 
  ring, 
  and 
  the 
  

   atrophied 
  radials, 
  e 
  and 
  d, 
  are 
  usually, 
  if 
  not 
  always, 
  fused 
  ; 
  basal 
  4 
  

   has 
  all 
  but 
  disappeared. 
  One 
  step 
  more 
  of 
  Atrophy, 
  and 
  all 
  trace 
  

   of 
  basal 
  4 
  and 
  of 
  the 
  spine 
  in 
  that 
  inter-radius 
  would 
  have 
  vanished 
  ; 
  

   one 
  step 
  more 
  of 
  Fusion, 
  and 
  radials 
  e 
  and 
  d 
  together 
  would 
  be, 
  to 
  

  

  Fig. 
  2. 
  — 
  Diagrams 
  illustrating 
  probable 
  Evolution 
  of 
  Trigonocrinus. 
  

  

  In 
  each 
  figure 
  the 
  corresponding 
  basals 
  are 
  numbered 
  1, 
  2, 
  3, 
  4, 
  5, 
  respectively, 
  

   and 
  the 
  corresponding 
  radials 
  lettered 
  a, 
  b, 
  c, 
  d, 
  e, 
  respectively 
  ; 
  the 
  numbers 
  

   are 
  arbitrary, 
  as 
  one 
  cannot 
  determine 
  the 
  true 
  orientation 
  of 
  these 
  fossils 
  ; 
  

   greater 
  depth 
  of 
  shading 
  indicates 
  greater 
  tendency 
  to 
  Hypertrophy, 
  less 
  

   depth 
  to 
  Atrophy: 
  — 
  I. 
  Primitive 
  iso-pentamerous 
  type, 
  cf. 
  Eugeniacr. 
  

   caryo'phyHatus. 
  II. 
  Loss 
  of 
  radial 
  b 
  and 
  basal 
  2 
  by 
  Sport, 
  producing 
  iso- 
  

   tetramerous 
  type, 
  cf. 
  Tetracrinus. 
  III. 
  Hypertrophy 
  of 
  radials 
  a, 
  c 
  and 
  

   basal 
  1. 
  Atrophy 
  of 
  basal 
  4 
  and, 
  to 
  a 
  less 
  extent, 
  of 
  the 
  remaining 
  calycal 
  

   elements. 
  IV. 
  Atrophy 
  continued. 
  Fusion 
  in 
  part 
  of 
  radials 
  e, 
  d, 
  and 
  

   complete 
  of 
  basals 
  1, 
  3, 
  5. 
  Trigonocrinus-stage. 
  V. 
  Complete 
  Fusion 
  of 
  

   radials 
  e, 
  d, 
  and 
  final 
  Atrophy 
  of 
  basal 
  4. 
  Future 
  stage. 
  

  

  all 
  appearance, 
  the 
  equivalent 
  of 
  either 
  a 
  or 
  c. 
  Such 
  a 
  form, 
  of 
  

   which 
  V 
  gives 
  the 
  scheme, 
  would 
  doubtless 
  have 
  been 
  described 
  as 
  

   " 
  a 
  triradiate 
  crinoid 
  ! 
  " 
  — 
  assuming 
  that 
  it 
  were 
  recognized 
  as 
  a 
  

   crinoid 
  at 
  all. 
  

  

  