﻿art 
  9 
  UNUSUAL 
  FORMS 
  OF 
  FOSSIL 
  CFJNOIDS 
  SPRINGER 
  O 
  

  

  some 
  well 
  marked 
  differences 
  in 
  the 
  details 
  of 
  the 
  columnals 
  and 
  

   cirri, 
  which 
  furnish 
  excellent 
  specific 
  characters, 
  it 
  is 
  not 
  practicable 
  

   to 
  correlate 
  them 
  with 
  other 
  characters 
  to 
  form 
  larger 
  groups; 
  and 
  

   as 
  to 
  the 
  stem 
  itself, 
  its 
  superficial 
  aspect 
  in 
  some 
  of 
  the 
  Silurian 
  

   forms 
  closely 
  approximates 
  that 
  in 
  some 
  from 
  the 
  Lower 
  Carboni- 
  

   ferous. 
  

  

  So 
  far 
  as 
  can 
  be 
  ascertained, 
  the 
  crown 
  in 
  the 
  Silurian 
  and 
  Lower 
  

   Devonian 
  forms 
  is 
  of 
  irregular 
  composition, 
  more 
  or 
  less 
  deformed 
  — 
  

   induced 
  perhaps 
  by 
  the 
  restricted 
  mode 
  of 
  life 
  of 
  the 
  crinoid 
  — 
  and 
  

   of 
  Heterocrinid 
  type. 
  In 
  some 
  of 
  the 
  Carboniferous 
  species 
  the 
  

   crown, 
  while 
  otherwise 
  regular, 
  is 
  somewhat 
  deformed 
  by 
  pressure. 
  

  

  It 
  would 
  appear 
  probable, 
  therefore, 
  that 
  this 
  peculiar 
  modifica- 
  

   tion 
  of 
  stem 
  structure 
  is 
  a 
  secondary 
  character, 
  arising 
  from 
  some 
  

   special 
  condition 
  of 
  life, 
  which 
  may 
  be 
  repeated 
  independently 
  

   without 
  materially 
  influencing 
  the 
  primary 
  characters 
  upon 
  which 
  

   genera 
  and 
  families 
  are 
  founded, 
  and 
  therefore 
  of 
  minor 
  taxonomic 
  

   importance 
  as 
  compared 
  with 
  the 
  great 
  alteration 
  in 
  the 
  superficial 
  

   appearance 
  of 
  the 
  organism 
  which 
  results 
  from 
  it. 
  

  

  The 
  Silurian 
  form 
  of 
  the 
  crinoid 
  with 
  coiled 
  stem 
  was 
  first 
  de- 
  

   scribed 
  by 
  Hall 
  in 
  1852 
  3 
  under 
  the 
  name 
  Myelodactylus, 
  based 
  upon 
  

   fragmentary 
  specimens 
  from 
  the 
  Rochester 
  shale 
  which 
  he 
  took 
  to 
  

   be 
  parts 
  of 
  arms. 
  In 
  1873 
  Salter 
  4 
  described 
  a 
  British 
  species 
  show- 
  

   ing 
  the 
  true 
  relation 
  of 
  the 
  crown 
  to 
  the 
  stem, 
  for 
  which 
  he 
  proposed 
  

   the 
  name 
  Herpetoerinus. 
  Angelin- 
  in 
  the 
  Iconographia, 
  1878, 
  de- 
  

   scribed 
  three 
  species 
  from 
  Gotland 
  under 
  Hall's 
  name; 
  and 
  in 
  1893 
  

   Bather, 
  in 
  the 
  Crinoidea 
  of 
  Gotland 
  (p. 
  36 
  and 
  following), 
  revised 
  the 
  

   whole 
  subject, 
  redescribing 
  Salter's 
  species, 
  rejecting 
  all 
  of 
  Angelin's, 
  

   and 
  adding 
  three 
  new 
  ones 
  of 
  his 
  own. 
  He 
  gave 
  a 
  full 
  summary 
  of 
  

   all 
  the 
  literature, 
  together 
  with 
  a 
  minute 
  account 
  of 
  the 
  morphology 
  

   of 
  the 
  stem, 
  with 
  elaborate 
  illustrations 
  which 
  for 
  beauty 
  of 
  execu- 
  

   tion 
  and 
  fulness 
  of 
  detail 
  leave 
  nothing 
  to 
  be 
  desired. 
  He 
  adopted 
  

   Salter's 
  name 
  Herpetocrinus, 
  rejecting 
  Hall's 
  Myelodactylus 
  because 
  

   he 
  thought 
  it 
  misleading 
  and 
  based 
  upon 
  incorrect 
  interpretation 
  of 
  

   the 
  structure. 
  In 
  1895, 
  in 
  an 
  article 
  in 
  the 
  American 
  Geologist 
  (vol. 
  

   16, 
  p. 
  213) 
  Doctor 
  Bather 
  again 
  discussed 
  Herpetocrinm 
  in 
  con- 
  

   nection 
  with 
  Brachiocrinus, 
  another 
  genus 
  of 
  Hall, 
  which 
  he 
  rightly 
  

   considered 
  to 
  be 
  of 
  the 
  same 
  type, 
  but 
  which 
  he 
  also 
  rejected 
  because, 
  

   as 
  in 
  his 
  first 
  genus, 
  Hall 
  had 
  mistaken 
  his 
  specimens 
  for 
  arm 
  frag- 
  

   ments 
  instead 
  of 
  stem. 
  

  

  Hall's 
  description 
  of 
  Myelodactylus, 
  however 
  erroneously 
  con- 
  

   ceived 
  as 
  to 
  the 
  nature 
  of 
  the 
  specimens, 
  was 
  accompanied 
  by 
  good 
  

   figures, 
  by 
  which 
  not 
  only 
  the 
  generic 
  type, 
  but 
  also 
  the 
  two 
  species 
  

  

  3 
  Paleontology 
  of 
  New 
  York, 
  vol. 
  2, 
  p. 
  191. 
  

  

  4 
  Catalog 
  fossils 
  in 
  the 
  Geological 
  Museum, 
  Cambridge, 
  p. 
  118. 
  

  

  