﻿crick: 
  on 
  AjnroxiTOCEBAs 
  tovilexse. 
  119 
  

  

  a 
  slight 
  flattening 
  or 
  even 
  a 
  slight 
  depression 
  on 
  the 
  central 
  part 
  

   of 
  the 
  peripheral 
  area. 
  The 
  rib 
  connecting 
  each 
  pair 
  of 
  tubercles 
  

   becomes 
  gradually 
  stronger 
  until, 
  where 
  the 
  diameter 
  is 
  350 
  nun., 
  

   most 
  of 
  the 
  fine 
  ribs 
  of 
  the 
  test 
  have 
  disappeared, 
  the 
  outer 
  tubercle 
  

   becomes 
  more 
  compressed 
  and 
  gradually 
  approaches 
  the 
  periphery 
  ; 
  

   the 
  three 
  ribs 
  connecting 
  it 
  with 
  its 
  fellow 
  on 
  the 
  opposite 
  side 
  are 
  

   relatively 
  coarser 
  and 
  liave 
  an 
  orad 
  convex 
  curve. 
  Later 
  the 
  finer 
  

   ornaments 
  disappear 
  except 
  on 
  the 
  inner 
  area 
  of 
  the 
  whorl, 
  aTid 
  the 
  

   shell 
  is 
  ornamented 
  with 
  strong 
  compressed 
  ribs, 
  which 
  encircle 
  the 
  

   whorl, 
  have 
  a 
  strong 
  projection 
  both 
  at 
  the 
  umbilical 
  margin 
  and 
  at 
  

   the 
  margin 
  of 
  the 
  peripliery, 
  and 
  a 
  slight 
  depression 
  at 
  the 
  middle 
  of 
  

   the 
  peripliery. 
  Tlie 
  body-cliamber 
  began 
  at 
  a 
  point 
  where 
  the 
  shell 
  

   liad 
  a 
  diameter 
  of 
  295 
  mm. 
  and 
  occupied 
  fully 
  three-fourths 
  of 
  the 
  

   last 
  whorl. 
  At 
  the 
  base 
  of 
  tlie 
  body-chamber 
  the 
  thickness 
  (or 
  width) 
  

   and 
  height 
  of 
  tlie 
  wliorl 
  are 
  about 
  135 
  mm. 
  and 
  115 
  ram. 
  respectively. 
  

   The 
  aperture 
  is 
  not 
  preserved. 
  The 
  details 
  of 
  tlie 
  septal-suture 
  are 
  

   unknown. 
  On 
  the 
  earliest 
  part 
  of 
  the 
  outer 
  whorl 
  and 
  immediately 
  

   in 
  front 
  of 
  the 
  aperture 
  the 
  periphery 
  is 
  broken 
  and 
  exposes 
  tlie 
  

   siphuncle 
  in 
  the 
  median 
  line 
  just 
  beneath 
  the 
  surface 
  in 
  two 
  places 
  

   (see 
  fig. 
  2) 
  ; 
  in 
  one 
  place 
  for 
  a 
  length 
  of 
  about 
  78 
  mm., 
  and 
  in 
  the 
  otlier 
  

   lor 
  a 
  length 
  of 
  about 
  23 
  mm. 
  ; 
  here 
  the 
  diameter 
  of 
  the 
  sipliuncle 
  is 
  

   about 
  4'5 
  mm. 
  

  

  In 
  a 
  Avork 
  by 
  Emilien 
  Dumas,' 
  pul)lis]ied 
  (1875-6) 
  after 
  the 
  

   author's 
  death, 
  an 
  ammonoid 
  from 
  the 
  Lower 
  Aptian 
  of 
  the 
  

   department 
  of 
  Gard 
  (France) 
  is 
  quoted 
  (but 
  not 
  described) 
  and 
  

   figured 
  as 
  Ammonitocerm 
  ucetice,"^ 
  other 
  cephalopods 
  occurring 
  at 
  the 
  

   same 
  liorizon 
  being 
  verj- 
  large 
  examjiles 
  of 
  Ancylocerasmatheronianum, 
  

   A. 
  gigas, 
  Nautilus 
  radiatus, 
  N. 
  piicafus, 
  Ammonites 
  stohieclcii, 
  and 
  

   Am. 
  crassicostatus. 
  

  

  The 
  genus 
  Ammonitoceras 
  was 
  not 
  described, 
  but 
  the 
  following 
  

   extract 
  from 
  the 
  notes 
  of 
  Emilien 
  Dumas 
  was 
  given 
  in 
  a 
  footnote 
  by 
  

   the 
  editor 
  of 
  the 
  work 
  (Lombard-Dumas) 
  : 
  " 
  Ce 
  nouveau 
  genre 
  doit 
  

   etre 
  place 
  entre 
  les 
  Ammonites 
  et 
  les 
  Scaphites. 
  II 
  se 
  rapproche 
  des 
  

   Ammonites 
  par 
  sa 
  coquille 
  enroulee 
  en 
  spirale 
  reguliere 
  dans 
  un 
  meme 
  

   plan 
  et 
  a 
  tours 
  en 
  contact 
  pendant 
  la 
  periode 
  erabryonnaire 
  et 
  la 
  

   periode 
  d'accroissement 
  ; 
  mais 
  a 
  I'age 
  adulte, 
  le 
  dernier 
  tour 
  se 
  

   detache 
  peu 
  a 
  peu 
  des 
  tours 
  reguliers 
  et 
  sa 
  projette 
  en 
  avant 
  en 
  

   conservant 
  toujours 
  une 
  forme 
  anjuee 
  au 
  lieu 
  de 
  se 
  prolonger 
  en 
  ligne 
  

   droite 
  comme 
  dans 
  les 
  Scaphites." 
  

  

  In 
  a 
  note 
  communicated 
  to 
  tlie 
  Geological 
  Society 
  of 
  France 
  on 
  the 
  

   19th 
  December, 
  1910, 
  Professor 
  W. 
  Kilian* 
  noticed 
  the 
  occurrence 
  of 
  

   a 
  gi'oup 
  of 
  loosely-coiled 
  ammonoids 
  in 
  the 
  Aptian 
  of 
  France, 
  of 
  the 
  

   Caucasus, 
  and 
  of 
  vai'ious 
  other 
  regions, 
  in 
  which 
  the 
  ornaments 
  differ 
  

   botli 
  from 
  those 
  of 
  Crioceras 
  (sensu 
  stficto) 
  and 
  of 
  Ancyloceras 
  (sensu 
  

   stricto) 
  by 
  the 
  possession 
  of 
  only 
  two 
  rows 
  of 
  lateral 
  tubercles 
  

  

  ' 
  Emilien 
  Dumas, 
  Statistique 
  geologique, 
  miner 
  alogiqice, 
  inetallurgique 
  et 
  

   paUontologique 
  clu 
  cUpartevient 
  du 
  Gard, 
  2 
  parts, 
  1875-6. 
  

  

  2 
  Op. 
  cit., 
  p. 
  405, 
  pi. 
  v, 
  figs. 
  1, 
  2. 
  

  

  ^ 
  W. 
  Kilian," 
  Sur 
  le 
  genre 
  Ammonitoceras 
  " 
  : 
  Bull. 
  Soc. 
  geol. 
  France, 
  ser. 
  iv, 
  

   vol. 
  X, 
  1912, 
  pp. 
  798-9. 
  

  

  