﻿ON 
  TRIGONOCRINUS 
  PROM 
  THE 
  " 
  WEISSER 
  JURA 
  " 
  OF 
  BAVARIA. 
  149 
  

  

  9. 
  Trigonocrinus, 
  anew 
  Genus 
  of 
  Crinoidea, 
  from 
  the 
  " 
  Weibser 
  

   Jura" 
  of 
  Bavaria; 
  with 
  the 
  Description 
  of 
  a 
  new 
  Species, 
  

   T. 
  liratus. 
  — 
  Appendix. 
  Sudden 
  Deviations 
  from 
  Normal 
  

   Symmetry 
  in 
  Neocrinoidea. 
  By 
  F. 
  A. 
  Bather, 
  Esq., 
  B.A., 
  

   F.G.S., 
  of 
  the 
  British 
  Museum 
  (Natural 
  History). 
  (Read 
  

   December 
  19, 
  1888.) 
  

  

  [Plate 
  VI.] 
  

   Locality 
  and 
  Horizon. 
  

  

  The 
  National 
  Collection 
  contains 
  a 
  large 
  amount 
  of 
  material 
  from 
  the 
  

   White 
  Jura 
  of 
  Wiirtemberg 
  and 
  Bavaria. 
  The 
  exact 
  horizon 
  and 
  

   locality 
  of 
  the 
  specimens 
  is 
  often 
  doubtful. 
  Several 
  hundred 
  calyces 
  of 
  

   Eugeniacrinus, 
  chiefly 
  E.caryophyllatus, 
  together 
  with 
  some 
  thousand 
  

   stem-fragments 
  of 
  the 
  same 
  genus, 
  are 
  said 
  to 
  come 
  from 
  Streitberg, 
  

   which 
  is 
  a 
  locality 
  for 
  Upper 
  Oxfordian 
  fossils 
  in 
  the 
  district 
  of 
  Ober 
  

   Pranken. 
  In 
  sorting 
  this 
  abundant 
  material 
  the 
  two 
  specimens 
  

   that 
  I 
  now 
  propose 
  to 
  describe 
  were 
  found. 
  The 
  remains 
  in 
  question 
  

   consist 
  of 
  calcspar 
  tinged 
  a 
  dirty 
  yellow 
  ; 
  they 
  appear 
  to 
  have 
  been 
  

   washed 
  out 
  of 
  a 
  yellowish 
  marly 
  matrix. 
  They 
  probably 
  occurred 
  

   in 
  the 
  same 
  bed 
  as 
  the 
  Eugeniacrini 
  ; 
  and, 
  after 
  a 
  comparison 
  with 
  

   fossils 
  in 
  continental 
  museums, 
  I 
  am 
  inclined 
  to 
  refer 
  them 
  to 
  the 
  

   " 
  Weisser 
  Jura 
  a." 
  It 
  is 
  greatly 
  to 
  be 
  regretted 
  that 
  no 
  more 
  certain 
  

   evidence 
  is 
  available. 
  

  

  Description 
  oe 
  the 
  Specimens. 
  

  

  Imagine 
  an 
  amphora 
  of 
  triangular 
  section, 
  with 
  an 
  " 
  ear 
  " 
  at 
  

   each 
  corner 
  in 
  the 
  shape 
  of 
  a 
  spine, 
  the 
  mouth 
  fairly 
  broad, 
  the 
  

   bottom 
  broken 
  off, 
  and 
  the 
  whole 
  only 
  4 
  mm. 
  high. 
  Such 
  gives 
  a 
  

   fair 
  idea 
  of 
  these 
  singular 
  fossils. 
  It 
  will 
  be 
  convenient 
  to 
  distin- 
  

   guish 
  the 
  two 
  specimens 
  as 
  A 
  and 
  B. 
  

  

  Specimen 
  A 
  is 
  the 
  more 
  perfect 
  of 
  the 
  two, 
  especially 
  at 
  the 
  lower 
  

   or 
  aboral 
  end. 
  

  

  There 
  is 
  no 
  trace 
  of 
  a 
  Stem 
  in 
  the 
  specimen, 
  nor 
  are 
  there 
  obvious 
  

   signs 
  of 
  a 
  sutural 
  surface 
  on 
  the 
  aboral 
  ends 
  of 
  the 
  basals 
  ; 
  the 
  

   large 
  size, 
  however, 
  of 
  the 
  aperture 
  at 
  the 
  base 
  of 
  the 
  calycal 
  cavity 
  

   (PL 
  YI. 
  fig. 
  4), 
  though 
  it 
  need 
  not 
  have 
  corresponded 
  to 
  a 
  large 
  

   axial 
  canal, 
  seems 
  to 
  prove 
  the 
  presence 
  of 
  at 
  least 
  some 
  stem 
  in 
  

   the 
  living 
  animal. 
  

  

  The 
  Basals 
  are 
  four 
  in 
  number 
  and 
  are 
  of 
  three 
  sizes. 
  The 
  

   largest 
  is 
  but 
  very 
  little 
  stouter 
  than 
  the 
  two 
  next 
  it 
  in 
  size 
  ; 
  the 
  

   second 
  and 
  third 
  are 
  equal 
  to 
  one 
  another, 
  and 
  lie 
  one 
  on 
  each 
  side 
  

   of 
  the 
  largest 
  ; 
  the 
  fourth, 
  or 
  smallest, 
  is 
  extremely 
  minute 
  and 
  

   cannot 
  be 
  distinguished 
  by 
  the 
  naked 
  eye. 
  These 
  basals 
  are 
  

   anchylosed 
  into 
  a 
  solid 
  ring, 
  which, 
  looked 
  at 
  from 
  below 
  (PL 
  YI. 
  

   fig. 
  4), 
  forms 
  an 
  almost 
  equilateral 
  triangle 
  ; 
  the 
  largest 
  basal 
  lies 
  

   at 
  the 
  apex, 
  the 
  second 
  and 
  third 
  basals 
  at 
  the 
  other 
  angles, 
  while 
  

   the 
  smallest 
  basal 
  lies 
  between 
  the 
  second 
  and 
  third 
  in 
  the 
  middle 
  

  

  