﻿118 
  

  

  ON 
  AMMONITOCERAS 
  TOVILENSE 
  FROM 
  THE 
  LOWER 
  

   GREENSAND 
  (APTIAN) 
  OF 
  KENT.' 
  

  

  By 
  G,. 
  C. 
  Crick, 
  F.G.S., 
  etc. 
  

  

  Bead 
  9th 
  June, 
  1916. 
  

  

  PLATE 
  VL 
  

  

  The 
  specimen 
  which 
  forms 
  the 
  subject 
  of 
  the 
  present 
  note 
  belongs 
  

   to 
  tbe 
  Britisli 
  Museum 
  collection 
  [B.M., 
  No. 
  C. 
  14671] 
  and 
  came 
  

   from 
  the 
  Hythe 
  Beds 
  of 
  the 
  Lower 
  Greensand 
  (Aptiaii) 
  at 
  Tovil, 
  

   near 
  Maidstone, 
  Kent. 
  When 
  obtained 
  only 
  a 
  portion 
  of 
  the 
  outer 
  

   wliorl 
  of 
  the 
  specimen 
  was 
  visible, 
  the 
  rest 
  being 
  covered 
  by 
  extremely 
  

   hard 
  matrix; 
  the 
  greater 
  part 
  of 
  this, 
  however, 
  has 
  been 
  successfully 
  

   removed 
  by 
  Mr. 
  Richard 
  Hall, 
  one 
  of 
  the 
  formatores 
  at 
  the 
  Museum, 
  

   and 
  to 
  him 
  therefore 
  we 
  are 
  indebted 
  iu 
  no 
  small 
  degree 
  for 
  the 
  

   admirable 
  specimen 
  described 
  below.' 
  

  

  The 
  fossil 
  is 
  fairly 
  complete 
  ; 
  the 
  body-chamber 
  occupies 
  about 
  

   three-fourths 
  of 
  the 
  last 
  whorl, 
  but 
  the 
  aperture 
  is 
  not 
  preserved. 
  

   The 
  shell 
  is 
  evolute, 
  the 
  whorls 
  being 
  just 
  in 
  contact. 
  Unfortunately 
  

   the 
  youngest 
  part 
  of 
  the 
  shell 
  is 
  not 
  exposed 
  and 
  may 
  not 
  be 
  

   preserved; 
  the 
  sliell 
  begins 
  where 
  the 
  coil 
  has 
  a 
  diameter 
  of 
  about 
  

   55 
  mm., 
  and 
  three 
  whorls 
  are 
  preserved. 
  The 
  diameter 
  of 
  the 
  whole 
  

   specimen 
  is 
  about 
  510 
  mm. 
  (about 
  20 
  inches), 
  the 
  width 
  of 
  the 
  

   umbilicus 
  (measured 
  from 
  suture 
  to 
  suture) 
  225 
  mm., 
  and 
  the 
  height 
  

   of 
  the 
  outer 
  whorl 
  about 
  164 
  mm. 
  The 
  whorls 
  are 
  subcircular 
  in 
  

   cross-section, 
  wider 
  than 
  high, 
  and 
  increase 
  rapidly. 
  At 
  a 
  point 
  

   about 
  100 
  mm. 
  (measured 
  along 
  the 
  median 
  line 
  of 
  the 
  ])eriphery) 
  

   from 
  the 
  anterior 
  end 
  of 
  the 
  specimen 
  the 
  thickness 
  of 
  the 
  whorl 
  

   including 
  the 
  rib 
  is 
  186 
  mm., 
  and 
  excluding 
  the 
  rib 
  170 
  mm., 
  whilst 
  

   the 
  height 
  of 
  the 
  whorl 
  including 
  the 
  rib 
  is 
  160 
  mm. 
  The 
  earliest 
  

   part 
  of 
  tlie 
  surface 
  of 
  the 
  specimen 
  is 
  much 
  damaged, 
  and 
  the 
  precise 
  

   nature 
  of 
  the 
  ornaments 
  cannot 
  be 
  seen 
  until 
  tlie 
  shell 
  has 
  attained 
  

   a 
  diameter 
  of 
  132 
  mm. 
  Here 
  the 
  test 
  is 
  ornamented 
  with 
  coarse 
  

   rounded 
  ribs 
  separated 
  by 
  intervals 
  rather 
  wider 
  than 
  the 
  ribs 
  ; 
  the 
  

   ribs 
  are 
  somewhat 
  reclined 
  over 
  the 
  greater 
  part 
  of 
  the 
  lateral 
  area, 
  

   and 
  at 
  the 
  umbilical 
  margin 
  of 
  the 
  whorl 
  curve 
  a 
  little 
  more 
  forward 
  

   as 
  far 
  as 
  the 
  suture 
  of 
  the 
  shell. 
  From 
  the 
  point 
  where 
  the 
  shell 
  has 
  

   a 
  diameter 
  of 
  132 
  mm. 
  the 
  whorl 
  exhibits 
  at 
  intervals 
  a 
  double 
  row 
  of 
  

   tubercles, 
  a 
  fairly 
  sharp 
  one 
  on 
  the 
  umbilical 
  margin 
  and 
  a 
  larger, 
  

   more 
  obtuse 
  one 
  on 
  about 
  the 
  middle 
  of 
  the 
  lateral 
  area. 
  Between 
  

   the 
  umbilical 
  tubercle 
  and 
  the 
  suture 
  of 
  the 
  shell 
  there 
  are 
  sometimes 
  

   two 
  ribs, 
  at 
  other 
  times 
  ov.lj 
  one, 
  rather 
  stouter 
  than 
  the 
  rest. 
  Each 
  

   pair 
  of 
  tubercles 
  is 
  connected 
  mostly 
  by 
  three 
  prominent 
  ribs, 
  and 
  

   from 
  the 
  outer 
  tubercle 
  there 
  are 
  usually 
  three 
  ribs 
  passing 
  over 
  the 
  

   periplierj'^ 
  of 
  the 
  whorl, 
  without 
  interruption, 
  though 
  sometimes 
  with 
  

  

  ^ 
  Published 
  by 
  permission 
  of 
  the 
  Trustees 
  of 
  the 
  British 
  Museum 
  (Nat. 
  Hist.). 
  

   ^ 
  In 
  its 
  present 
  condition, 
  after 
  development, 
  the 
  fossil 
  weighs 
  almost 
  exactly 
  

   100 
  lb. 
  

  

  