﻿386 
  G, 
  H. 
  VINE 
  ON 
  THE 
  ANNELIDA 
  TtTBICOLA 
  

  

  institute 
  the 
  comparison 
  that 
  I 
  should 
  wish. 
  If 
  it 
  be 
  placed 
  with 
  

   Theca 
  of 
  Morris, 
  a 
  synonym 
  of 
  which 
  is 
  the 
  Creseis 
  of 
  Forbes, 
  then 
  

   the 
  nearest 
  approach 
  to 
  the 
  type 
  is 
  the 
  Atlantic 
  species 
  C. 
  aciculata, 
  

   Rang 
  ; 
  but 
  in 
  this 
  type, 
  as 
  figured 
  in 
  "Woodward's 
  ; 
  Manual 
  of 
  the 
  

   Mollusca 
  ' 
  (pi. 
  14. 
  fig. 
  34), 
  there 
  is 
  no 
  appearance 
  of 
  annulations, 
  and 
  

   this 
  is 
  one 
  of 
  the 
  chief 
  peculiarities 
  of 
  Tentaculites. 
  

  

  The 
  material 
  for 
  a 
  complete 
  study 
  of 
  this 
  group, 
  irrespective 
  of 
  

   its 
  zoological 
  affinities, 
  is 
  afforded 
  by 
  specimens 
  in 
  the 
  shales. 
  I 
  

   do 
  not 
  think 
  I 
  am 
  justified 
  in 
  placing 
  upon 
  record 
  more 
  than 
  four 
  

   species 
  as 
  prevalent 
  in 
  the 
  washings 
  ; 
  but 
  their 
  remains 
  are 
  so 
  abun- 
  

   dant, 
  and 
  so 
  well 
  preserved, 
  that 
  sections 
  of 
  the 
  shells 
  afford 
  reliable 
  

   evidence 
  as 
  to 
  their 
  special 
  structure 
  ; 
  and 
  I 
  must 
  be 
  pardoned 
  if 
  I 
  

   step 
  a 
  little 
  beyond 
  the 
  purely 
  geological 
  for 
  the 
  purpose 
  of 
  showing 
  

   the 
  microscopical 
  evidence 
  which 
  the 
  sections 
  reveal. 
  When 
  the 
  

   facts 
  are 
  formulated, 
  a 
  comparison 
  can 
  be 
  made 
  between 
  the 
  shells 
  

   of 
  Tentaculites 
  and 
  recent 
  Pteropoda. 
  I 
  have 
  been 
  deceived 
  so 
  

   often 
  in 
  the 
  mere 
  external 
  features 
  of 
  Pahcozoic 
  fossils 
  when 
  making 
  

   a 
  comparison 
  with 
  recent 
  apparently 
  allied 
  types, 
  that 
  I 
  feel 
  certain 
  

   a 
  check 
  upon 
  hasty 
  conclusions 
  will 
  be 
  of 
  the 
  same 
  value 
  in 
  re- 
  

   searches 
  of 
  this 
  kind 
  to 
  others 
  as 
  to 
  me. 
  There 
  are 
  other 
  inves- 
  

   tigations 
  outside 
  of 
  the 
  pale 
  of 
  pakeontological 
  inquiries 
  which 
  

   must 
  act 
  as 
  factors 
  in 
  the 
  lines 
  of 
  research, 
  as 
  well 
  as 
  mere 
  mor- 
  

   phological 
  details, 
  and 
  these 
  must 
  come 
  in 
  to 
  help 
  in 
  the 
  decision 
  

   as 
  to 
  the 
  zoological 
  affinities 
  of 
  fossil 
  types. 
  I 
  refer 
  now 
  espe- 
  

   cially 
  to 
  the 
  masterlv 
  address 
  of 
  Dr. 
  Sorby 
  to 
  the 
  Geological 
  Society 
  

   in 
  1879. 
  

  

  In 
  this 
  address 
  Dr. 
  Sorby 
  refers 
  to 
  the 
  mineral 
  constituents 
  of 
  

   certain 
  shells, 
  and 
  he 
  says 
  that 
  " 
  this 
  difference 
  in 
  the 
  state 
  of 
  pre- 
  

   servation 
  of 
  fossils, 
  according 
  as 
  they 
  were 
  originally 
  composed 
  of 
  

   calcite 
  or 
  of 
  aragonite, 
  appears 
  to 
  be 
  so 
  well 
  established 
  in 
  all 
  thoso 
  

   cases 
  in 
  which 
  we 
  are 
  able 
  to 
  ascertain 
  the 
  true 
  mineral 
  nature 
  of 
  

   closely 
  allied 
  living 
  organisms, 
  that 
  I 
  feel 
  myself 
  justified 
  in 
  con- 
  

   cluding 
  that 
  certain 
  doubtful 
  fossil 
  forms 
  were 
  originally 
  calcite, 
  

   because 
  they 
  arc 
  preserved 
  like 
  those 
  in 
  the 
  same 
  thin 
  section 
  known 
  

   to 
  have 
  been 
  so 
  ; 
  whilst 
  those 
  known 
  to 
  have 
  been 
  aragonite 
  have 
  

   become 
  quite 
  crystalline 
  aud 
  lost 
  their 
  original 
  structure"*. 
  Of 
  

   Annelida 
  Tubicola 
  he 
  says, 
  " 
  probably 
  calcite, 
  but 
  they 
  include 
  

   many 
  foreign 
  fragments" 
  f. 
  Further 
  on, 
  again, 
  he 
  says 
  " 
  The 
  shell 
  

   has 
  usually 
  a 
  more 
  or 
  less 
  distinct 
  laminar 
  structure 
  parallel 
  to 
  the 
  

   surface 
  of 
  growth. 
  The 
  calcite 
  is 
  in 
  the 
  form 
  of 
  minute 
  granules, 
  

   often 
  without 
  any 
  definite 
  optical 
  orientation 
  " 
  %. 
  As 
  the 
  Tentacu- 
  

   lites, 
  which 
  will 
  be 
  referred 
  to 
  again, 
  do 
  retain 
  their 
  original 
  struc- 
  

   ture, 
  we 
  may 
  reasonably 
  suppose 
  that 
  the 
  shell 
  at 
  least 
  was 
  com- 
  

   posed 
  of 
  calcite. 
  I 
  hope 
  that 
  these 
  special 
  mineralogical 
  details 
  will 
  

   assist 
  in 
  guiding 
  our 
  judgment 
  as 
  to 
  the 
  proper 
  zoological 
  position 
  

   of 
  these 
  unique 
  Silurian 
  fossils, 
  as 
  well 
  as 
  the 
  more 
  special 
  and 
  mor- 
  

   phological 
  details 
  of 
  authors. 
  

  

  * 
  Dr. 
  Sorby's 
  Anniversary 
  Address, 
  Q. 
  J. 
  G. 
  S. 
  1879, 
  vol. 
  xxxv. 
  p. 
  68. 
  

   t 
  Ibid. 
  p. 
  60. 
  | 
  Ibid. 
  p. 
  63. 
  

  

  

  