﻿NEWTON 
  : 
  GEOLOGICAL 
  ZONES 
  AND 
  THEIR 
  MOLLUSCA. 
  289 
  

  

  Lias 
  differed 
  slightly 
  from 
  that 
  of 
  Oppel 
  and 
  Wright's 
  schemes, 
  

   inasmuch 
  as 
  he 
  regarded 
  Ammonites 
  capricornus 
  as 
  the 
  uppermost 
  

   zone 
  of 
  the 
  Lower 
  Lias 
  instead 
  of 
  raricostatus, 
  thus 
  following 
  

   Quenstedt's 
  views 
  in 
  connexion 
  with 
  the 
  Jurassic 
  subdivisions 
  of 
  

   Grermany. 
  Professor 
  Judd's 
  arrangement 
  of 
  the 
  Liassic 
  zones 
  is, 
  

   however, 
  the 
  one 
  adopted 
  by 
  the 
  Geological 
  Survey 
  of 
  this 
  country. 
  

   Its 
  zones, 
  in 
  descending 
  order, 
  are 
  as 
  follows 
  : 
  — 
  

  

  Upper 
  Lias 
  . 
  . 
  Ammonites 
  Jurensis, 
  communis. 
  

  

  Middle 
  Lias 
  . 
  A. 
  spinatus, 
  margaritatiis. 
  

  

  LoAVER 
  Lias. 
  . 
  A. 
  cajjrtcornus^?), 
  tbex{?), 
  Jcimesoni, 
  armatus, 
  

   oxi/fiotus, 
  oMustis, 
  semicostatus, 
  Bucldandi^ 
  

   angulatiis, 
  planorhis. 
  

  

  It 
  should 
  be 
  mentioned 
  here 
  that 
  Waagen 
  had 
  published 
  a 
  pre- 
  

   liminary 
  paper 
  in 
  1869^ 
  dealing 
  with 
  the 
  Ammonites 
  and 
  their 
  

   nomenclature, 
  in 
  which 
  it 
  was 
  suggested 
  that 
  the 
  term 
  Ammonites 
  

   should 
  no 
  longer 
  be 
  applicable 
  as 
  a 
  generic 
  name, 
  although 
  it 
  might 
  

   be 
  used 
  to 
  designate 
  a 
  group. 
  He 
  therefore 
  divided 
  these 
  Cephalopods 
  

   into 
  genera 
  and 
  sub-genera, 
  according 
  to 
  the 
  length 
  of 
  the 
  chamber 
  

   occupied 
  by 
  the 
  animal, 
  the 
  form 
  of 
  the 
  mouth, 
  the 
  characters 
  of 
  the 
  

   aptychus 
  when 
  present, 
  and 
  the 
  sculpture, 
  the 
  lobes 
  being 
  regarded 
  

   as 
  only 
  of 
  secondary 
  importance. 
  The 
  names 
  thus 
  established 
  were 
  : 
  

   ^goceras, 
  Arietites, 
  Am.aUheus, 
  Harpoceras, 
  Oppelia, 
  (Ekotraustes, 
  

   Stephanoceras, 
  Perispliinctes, 
  and 
  Cosmoceras. 
  

  

  Messrs. 
  Tate 
  & 
  Blake, 
  in 
  their 
  history 
  of 
  " 
  The 
  Yorkshire 
  Lias 
  " 
  

   of 
  1876, 
  recognized 
  the 
  following 
  Liassic 
  zones 
  in 
  that 
  county, 
  

   founded 
  upon 
  Ammonite 
  species: 
  — 
  

  

  iZone 
  of 
  Ammonites 
  Jurensis. 
  

   ,, 
  A. 
  communis. 
  

   ,, 
  A. 
  serpentmus. 
  

   ,, 
  A. 
  annulatus. 
  

   ,, 
  A. 
  spina 
  tus. 
  

   Middle 
  Lias 
  { 
  ,, 
  A. 
  margaritatiis. 
  

   ,, 
  A. 
  capricornus. 
  

   ,, 
  A. 
  Jamesoni. 
  

   I 
  ,, 
  A. 
  oxynotus. 
  

  

  T 
  -r 
  \ 
  ....A. 
  Buchlandi. 
  

  

  Lower 
  Lias 
  > 
  " 
  . 
  , 
  , 
  

  

  I 
  ,, 
  A. 
  anguiatus. 
  

  

  \ 
  ,, 
  A. 
  planorbis. 
  

  

  Rh^tic. 
  Avicula 
  contorta 
  Beds. 
  

  

  These 
  authors 
  adopted 
  the 
  new 
  generic 
  nomenclature 
  of 
  AVaagen 
  and 
  

  

  others 
  for 
  the 
  Ammonites 
  in 
  the 
  clescriptiA^e 
  part 
  of 
  their 
  work, 
  but 
  

  

  retained 
  the 
  terra 
  Ammojiites 
  in 
  the 
  generic 
  sense 
  for 
  stratigraphieal 
  

  

  purposes. 
  

  

  Some 
  years 
  later 
  Dr. 
  Wright- 
  published 
  his 
  great 
  Monograph 
  of 
  the 
  

  

  liias 
  Ammonites 
  of 
  the 
  British 
  Islands, 
  in 
  which 
  the 
  Lias 
  deposits 
  of 
  

  

  this 
  country 
  were 
  considered 
  as 
  corresponding 
  to 
  a 
  large 
  extent 
  with 
  

  

  ^ 
  Benecke's 
  Palaontologische 
  Beitrage, 
  vol. 
  ii, 
  pt. 
  ii, 
  1869 
  ; 
  a 
  fuller 
  treatment 
  

   of 
  the 
  same 
  subject 
  being 
  published 
  by 
  Waagen 
  the 
  year 
  following 
  in 
  the 
  

   Palseontographica, 
  vol. 
  xvii, 
  pp. 
  185-220, 
  1870. 
  

  

  " 
  Palaeontographical 
  Society, 
  1878-86. 
  

  

  