﻿166 
  

  

  PROCEEDINGS 
  

  

  OF 
  

  

  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  POSTPONED 
  PAPER. 
  

  

  A 
  Monograph 
  of 
  the 
  Ammonites 
  of 
  the 
  Cambridge 
  Greensand. 
  

   By 
  Harry 
  Seeley, 
  Esq., 
  F.Gr.S., 
  Woodwardian 
  Museum. 
  

  

  [Read 
  June 
  17, 
  1863*.] 
  

  

  [This 
  paper 
  was 
  withdrawn 
  by 
  permission 
  of 
  the 
  Council.] 
  

  

  (Abstract.) 
  

  

  In 
  this 
  paper 
  the 
  Ammonites 
  and 
  Scaphites 
  of 
  the 
  Cambridge 
  Co- 
  

   prolite-bed 
  were 
  described, 
  with 
  the 
  endeavour 
  to 
  elucidate 
  the 
  

   nature 
  of 
  Ammonite-species 
  in 
  a 
  single 
  stratum 
  and 
  a 
  limited 
  area. 
  

   It 
  was 
  the 
  result 
  of 
  five 
  years' 
  study 
  of 
  about 
  12,000 
  specimens. 
  

  

  The 
  special 
  peculiarity 
  of 
  the 
  paper 
  was 
  that 
  many 
  " 
  species" 
  

   hitherto 
  thought 
  distinct 
  were 
  connected 
  together. 
  This 
  was 
  called 
  

   " 
  resolving 
  species 
  into 
  the 
  varieties 
  of 
  which 
  they 
  appear 
  to 
  con- 
  

   sist." 
  The 
  specific 
  names 
  became 
  varietal, 
  " 
  the 
  idea 
  of 
  the 
  system 
  

   followed 
  being 
  to 
  make 
  certain 
  forms 
  the 
  indices 
  as 
  it 
  were 
  to 
  their 
  

   groups," 
  without 
  disturbing 
  the 
  existing 
  nomenclature. 
  

  

  There 
  are 
  three 
  " 
  great 
  species," 
  or 
  groups, 
  called 
  Ammonites 
  ros- 
  

   tratus, 
  A. 
  splendens, 
  and 
  A. 
  planulatus 
  ; 
  and 
  a 
  few 
  " 
  small 
  species," 
  

   mostly 
  new 
  ; 
  besides 
  these 
  were 
  a 
  small 
  group 
  of 
  Scaphites, 
  and 
  a 
  

   Crioceras 
  from 
  Hunstanton. 
  

  

  Every 
  recognizable 
  variation 
  of 
  form 
  was 
  described, 
  and, 
  in 
  a 
  few 
  

   marked 
  instances, 
  named, 
  the 
  named 
  forms 
  being 
  merely 
  used 
  as 
  

   necessary 
  links 
  for 
  connecting 
  together 
  allied 
  species. 
  

  

  In 
  the 
  " 
  splendens 
  group," 
  A. 
  Fittoni 
  was 
  shown 
  to 
  pass 
  insen- 
  

   sibly 
  into 
  A. 
  splendens. 
  A. 
  splendens 
  was 
  traced 
  on 
  the 
  one 
  hand 
  

   through 
  a 
  series 
  of 
  variations 
  into 
  a 
  thick 
  and 
  robust, 
  ribbed, 
  and 
  

   tubercled 
  new 
  species 
  called 
  A. 
  cratus 
  ; 
  and 
  this 
  again 
  was 
  regarded 
  

   as 
  passing 
  into 
  another 
  new 
  form, 
  very 
  thin 
  and 
  flat, 
  called 
  A. 
  leptus. 
  

   And, 
  on 
  the 
  other 
  hand, 
  A. 
  splendens 
  was 
  traced 
  into 
  A. 
  Guersantii, 
  

   and 
  A. 
  Guersantii 
  into 
  A. 
  Renausianus, 
  and 
  this 
  again 
  into 
  another 
  

   new 
  form 
  called 
  A. 
  gymnus. 
  A. 
  Guersantii 
  passed 
  into 
  A. 
  auritus 
  ; 
  

   this 
  species 
  passed 
  into 
  a 
  new 
  form 
  called 
  A. 
  novatus 
  ; 
  this 
  into 
  

  

  * 
  For 
  the 
  other 
  communications 
  read 
  at 
  this 
  Evening-meeting, 
  see 
  Quart. 
  

   Journ. 
  Geol. 
  Soc. 
  vol. 
  six. 
  p. 
  506, 
  and 
  vol. 
  xx. 
  p. 
  74. 
  

  

  