﻿art 
  9 
  UNUSUAL, 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  95 
  

  

  the 
  most 
  striking 
  of 
  these 
  forms, 
  M 
  onobrachmcrinus 
  with 
  one 
  arm, 
  

   and 
  Embryocrinus 
  armless, 
  are 
  very 
  abundant, 
  indicating 
  a 
  wide 
  

   extent 
  of 
  the 
  conditions 
  and 
  their 
  effects; 
  while 
  the 
  others 
  are 
  rare. 
  

   One 
  of 
  the 
  two 
  genera 
  with 
  aberrant 
  orals, 
  Goenocystis 
  Girty, 
  al- 
  

   ready 
  known 
  in 
  America, 
  is 
  represented 
  by 
  a 
  single 
  specimen, 
  which 
  

   might 
  be 
  attributed 
  to 
  malformation; 
  but 
  of 
  the 
  other 
  there 
  are 
  

   two 
  well 
  defined 
  specimens 
  in 
  which 
  the 
  exceptional 
  character 
  is 
  

   clearly 
  shown, 
  leaving 
  no 
  doubt 
  of 
  its 
  being 
  a 
  definite 
  structure. 
  

  

  Evidently 
  this 
  extreme 
  specialization 
  marked 
  the 
  end 
  of 
  the 
  line, 
  

   for 
  these 
  armless 
  crinoids 
  left 
  no 
  successors 
  to 
  our 
  knowledge, 
  

   either 
  in 
  the 
  prolific 
  deposits 
  of 
  the 
  Mesozoic, 
  or 
  among 
  the 
  

   numerous 
  species 
  which 
  inhabit 
  the 
  present 
  oceans. 
  But 
  there 
  are 
  

   certain 
  other 
  forms 
  which 
  seem 
  in 
  a 
  remarkable 
  way 
  to 
  anticipate 
  

   Mesozoic 
  types; 
  for 
  example, 
  the 
  genera 
  Prophyllocrinus 
  and 
  Pro- 
  

   apsidocrinus, 
  which 
  may 
  well 
  be 
  taken 
  as 
  the 
  ancestors 
  of 
  the 
  

   Jurassic 
  genera 
  from 
  which 
  their 
  names 
  are 
  adapted. 
  Equally 
  

   remarkable 
  as 
  a 
  survival, 
  or 
  a 
  prophetic 
  type, 
  or 
  more 
  probably 
  

   as 
  an 
  independent 
  example 
  of 
  adaptation 
  to 
  a 
  reef 
  life, 
  is 
  Palaeho- 
  

   lopus, 
  which 
  like 
  Edriocrinus 
  of 
  the 
  Devonian, 
  Cyathidium 
  of 
  the 
  

   Chalk, 
  and 
  Holopus 
  of 
  the 
  present 
  seas, 
  had 
  no 
  stem, 
  but 
  was 
  

   attached 
  directly 
  by 
  the 
  greatly 
  modified 
  base 
  to 
  rocks 
  or 
  corals 
  at 
  

   shallow 
  depths. 
  

  

  The 
  age 
  of 
  the 
  Timor 
  crinoids 
  and 
  Mastoids, 
  held 
  by 
  the 
  author 
  

   to 
  be 
  Permian, 
  remains 
  a 
  perplexing 
  question, 
  owing 
  to 
  the 
  presence 
  

   of 
  such 
  a 
  large 
  element 
  of 
  distinctly 
  Lower 
  Carboniferous 
  affini- 
  

   ties. 
  This 
  was 
  briefly 
  discussed 
  by 
  me, 
  57 
  and 
  somewhat 
  further 
  

   since. 
  58 
  While 
  it 
  is 
  admitted 
  that 
  much 
  remains 
  to 
  be 
  learned 
  con- 
  

   cerning 
  the 
  geology 
  of 
  Timor, 
  yet 
  in 
  view 
  of 
  the 
  concurrent 
  opinion 
  

   to 
  the 
  same 
  effect 
  of 
  the 
  other 
  authors 
  who 
  have 
  studied 
  the 
  asso- 
  

   ciated 
  invertebrate 
  fossils, 
  it 
  would 
  seem 
  that 
  the 
  Permian 
  age 
  of 
  

   the 
  formation 
  as 
  now 
  determined 
  should 
  be 
  accepted. 
  

  

  67 
  Smithson. 
  Misc. 
  Coll., 
  vol. 
  76, 
  1923, 
  p. 
  30. 
  

  

  58 
  Amer. 
  Journ. 
  Science, 
  vol. 
  8, 
  October, 
  1924, 
  p. 
  325 
  

  

  