﻿156 
  PROCEEDINGS 
  OF 
  THE 
  MALACOLOGICAL 
  SOCIETY. 
  

  

  To 
  this 
  description 
  he 
  adds 
  the 
  following 
  remarks 
  : 
  — 
  

  

  "About 
  three 
  whorls, 
  rapidly 
  increasing, 
  compose 
  this 
  Ammonite 
  : 
  

   all 
  the 
  costce 
  reach 
  the 
  edge 
  of 
  the 
  umbilicus, 
  half 
  or 
  more 
  of 
  them 
  

   turn 
  into 
  it, 
  and 
  at 
  the 
  same 
  time 
  are 
  rather 
  enlarged 
  ; 
  the 
  costse 
  

   and 
  the 
  spaces 
  between 
  them 
  are 
  nearly 
  equal. 
  

  

  " 
  From 
  the 
  lower 
  chalk 
  at 
  Guildford 
  : 
  pi'esented 
  to 
  Mrs. 
  Murchison 
  

   by 
  Mr. 
  Mantell. 
  It 
  is 
  only 
  half 
  the 
  size 
  of 
  the 
  one 
  figured 
  in 
  the 
  

   Geology 
  of 
  Sussex, 
  where 
  it 
  is 
  spoken 
  of 
  as 
  a 
  very 
  rare 
  shell." 
  

  

  It 
  is 
  unfortunate 
  that 
  the 
  precise 
  locality 
  of 
  Sowerby's 
  figured 
  

   specimen 
  is 
  not 
  recorded, 
  since 
  several 
  zones 
  of 
  the 
  Chalk 
  are 
  

   represented 
  in 
  the 
  neighbourhood 
  of 
  Guildford. 
  Thus, 
  according 
  to 
  

   the 
  Memoirs 
  of 
  the 
  Geological 
  Survey 
  on 
  the 
  Cretaceous 
  Kocks 
  of 
  

   Britain 
  (vol. 
  ii, 
  Lower 
  and 
  Middle 
  Chalk 
  of 
  England, 
  p. 
  55), 
  a 
  

   quarry 
  1^ 
  miles 
  south-east 
  of 
  Guildford 
  exposes 
  Lower 
  Chalk 
  with 
  

   the 
  Belemnite 
  Marls, 
  whilst 
  in 
  quarries 
  to 
  the 
  west 
  of 
  Guildford 
  the 
  

   Melbourn 
  Hock 
  (zone 
  of 
  Rhynchonella 
  cuvieri) 
  is 
  exposed 
  (vol. 
  ii, 
  

   Lower 
  and 
  Middle 
  Chalk 
  of 
  England, 
  p. 
  38()). 
  The 
  upper 
  part 
  of 
  

   the 
  Terebratulina 
  zone 
  is 
  seen 
  in 
  the 
  Shalford 
  quarries 
  south 
  of 
  

   Guildford 
  (vol. 
  ii. 
  Lower 
  and 
  Middle 
  Chalk 
  of 
  England, 
  p. 
  387), 
  and 
  

   an 
  old 
  disused 
  quarry, 
  about 
  a 
  mile 
  to 
  the 
  south-east 
  of 
  Guildford, 
  

   presenting 
  a 
  perpendicular 
  face 
  of 
  about 
  100 
  feet, 
  exhibits 
  the 
  

   succession 
  of 
  the 
  chalk 
  from, 
  and 
  including, 
  the 
  upper 
  part 
  of 
  the 
  

   Terehratulina 
  zone 
  (vol. 
  ii, 
  Lower 
  and 
  Middle 
  Chalk 
  of 
  England, 
  

   p. 
  387) 
  "through 
  the 
  zone 
  of 
  Ilolaster 
  planus 
  to 
  the 
  Upper 
  Chalk" 
  

   (vol. 
  iii, 
  the 
  Upper 
  Chalk 
  of 
  England, 
  p. 
  175). 
  At 
  Monkshatch, 
  

   about 
  5 
  miles 
  west 
  of 
  Guildford, 
  there 
  is 
  a 
  large 
  disused 
  quarry 
  

   showing 
  about 
  42 
  feet 
  of 
  the 
  Rolaster 
  planus 
  zone 
  resting 
  upon 
  about 
  

   30 
  feet 
  of 
  the 
  Terehratulina 
  zone 
  (vol. 
  iii, 
  the 
  Upper 
  Chalk 
  of 
  

   England, 
  p. 
  176), 
  whilst 
  Dr. 
  Barrels 
  thought 
  he 
  recognized 
  the 
  

   Marsupite 
  zone 
  on 
  the 
  north 
  side 
  of 
  the 
  Hog's 
  Back, 
  near 
  Guildford, 
  

   in 
  1876 
  [Recherches 
  sur 
  le 
  Terram 
  Cretace 
  superieur, 
  1876, 
  p. 
  139). 
  

   In 
  the 
  absence, 
  therefore, 
  of 
  pi'ecise 
  information 
  as 
  to 
  the 
  pit 
  from 
  

   which 
  the 
  fossil 
  was 
  obtained, 
  it 
  is 
  not 
  possible 
  to 
  say 
  from 
  what 
  

   horizon 
  Sowerby's 
  figured 
  specimen 
  came. 
  Further, 
  the 
  present 
  

   location 
  of 
  this 
  fossil 
  is 
  unknown 
  to 
  the 
  writer, 
  so 
  that 
  an 
  actual 
  

   comparison 
  with 
  Mantell's 
  type-specimen 
  is 
  not 
  possible. 
  

  

  We 
  think, 
  however, 
  that 
  there 
  is 
  great 
  reason 
  for 
  believing 
  Pictet* 
  

   to 
  be 
  right 
  in 
  considering 
  this 
  specimen 
  as 
  specifically 
  distinct 
  from 
  

   Mantell's 
  type-specimen. 
  He 
  considered 
  it 
  to 
  be 
  without 
  doubt 
  the 
  

   adult 
  of 
  a 
  slightly 
  compressed 
  form 
  of 
  Brongniart's 
  Ammonites 
  

   gentoni} 
  

  

  In 
  his 
  Description 
  of 
  the 
  Fossil 
  Remains 
  of 
  Mollusca 
  foimd 
  in 
  the 
  

   Chalk 
  of 
  England 
  (Mon. 
  Pal. 
  Soc), 
  Sharpe 
  figured 
  four 
  specimens 
  

   (pi. 
  xviii, 
  figs. 
  1, 
  2, 
  3, 
  and 
  5, 
  and 
  the 
  suture-line 
  fig. 
  8) 
  as 
  Ammonites 
  

   navicularis. 
  These 
  are 
  now 
  in 
  the 
  British 
  Museum 
  collection. 
  His 
  

   largest 
  example 
  [B.M. 
  No. 
  36834], 
  the 
  original 
  of 
  his 
  fig. 
  1, 
  has 
  

  

  ' 
  F. 
  J. 
  Pictet, 
  Mdanges 
  paUontologiques, 
  vol. 
  i, 
  livr. 
  1, 
  1863, 
  p. 
  33. 
  

   ^ 
  A. 
  Brongniart, 
  Descr. 
  des 
  environs 
  de 
  Paris, 
  in 
  Cuvier's 
  Recherches 
  

   Ossements 
  foss., 
  4me 
  ed., 
  torn, 
  iv, 
  1834, 
  p. 
  150, 
  pi. 
  N, 
  fig. 
  6). 
  

  

  