﻿170 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  The 
  constant 
  Middle-Lias 
  zonal 
  divisions 
  are 
  the 
  six 
  following 
  : 
  — 
  

  

  Amaliheus 
  spinatus, 
  represented 
  in 
  Britain, 
  Belgium, 
  Prance 
  (6 
  

   departments), 
  Switzerland, 
  Germany, 
  Austria, 
  

   Italy. 
  

   „ 
  margaritatus, 
  Britain, 
  Belgium, 
  France 
  (6 
  departments), 
  

   Switzerland, 
  Germany, 
  Austria, 
  Italy. 
  

  

  JZgoceras 
  Henleyi, 
  Britain, 
  Belgium, 
  Prance 
  (6 
  departments), 
  

   Switzerland, 
  Germany, 
  Austria, 
  Italy. 
  

  

  Amaliheus 
  ibex, 
  Britain, 
  Belgium, 
  Prance 
  (6 
  departments), 
  Swit- 
  

   zerland, 
  Germany, 
  Austria, 
  Italy. 
  

  

  JSgoceras 
  Jamesoni, 
  Britain, 
  Belgium, 
  Prance 
  (4 
  departments), 
  

   Switzerland, 
  Germany, 
  Austria, 
  Italy. 
  

   „ 
  armatum, 
  Britain, 
  Belgium, 
  Prance 
  (2 
  departments), 
  

   Switzerland, 
  Germany, 
  Austria, 
  Italy. 
  

  

  The 
  Upper-Lias 
  Ammonites 
  that 
  everywhere 
  characterize 
  similar 
  

   definite 
  horizons 
  are 
  the 
  four 
  following: 
  — 
  

  

  Harpoceras 
  opalinum, 
  England, 
  Scotland, 
  Belgium, 
  Prance, 
  Swit- 
  

   zerland, 
  Germany, 
  Austria, 
  Italy. 
  

  

  Lytoceras 
  jurense, 
  England, 
  Scotland, 
  Belgium, 
  France, 
  Switzer- 
  

   land, 
  Germany 
  Austria, 
  Italy. 
  

  

  Harpoceras 
  bifrons, 
  England, 
  Scotland, 
  Belgium, 
  Prance, 
  Swit- 
  

   zerland, 
  Germany, 
  Austria, 
  Italy. 
  

   „ 
  serpentinum, 
  England, 
  Scotland, 
  Belgium, 
  France, 
  

  

  Switzerland, 
  Austria, 
  Italy. 
  

  

  These 
  16 
  zones 
  in 
  the 
  Lias, 
  as 
  they 
  appear 
  in 
  time, 
  hold 
  a 
  special 
  

   fauna, 
  and 
  most 
  of 
  the 
  species 
  equally 
  characterize 
  the 
  horizon 
  in 
  

   which 
  they 
  occur. 
  The 
  whole 
  of 
  the 
  Secondary 
  rocks, 
  from 
  the 
  base 
  

   of 
  the 
  Lias 
  to 
  the 
  highest 
  Chalk, 
  have 
  thus 
  been 
  subdivided 
  and 
  

   specialized 
  by 
  the 
  Ammonitidas 
  — 
  a 
  classification 
  holding 
  good 
  for 
  

   Europe, 
  India, 
  and 
  America, 
  many 
  species 
  being 
  the 
  same 
  both 
  in 
  

   the 
  eastern 
  and 
  western 
  hemispheres 
  *. 
  

  

  The 
  whole 
  of 
  the 
  293 
  species 
  in 
  the 
  Lias 
  fall 
  under 
  these 
  sec- 
  

   tional 
  divisions. 
  A 
  careful 
  study 
  of 
  the 
  Table 
  (XXVI.) 
  devoted 
  to 
  

   the 
  analysis 
  of 
  the 
  Liassic 
  species 
  reveals 
  the 
  remarkable 
  fact 
  that, 
  

   with 
  the 
  exception 
  of 
  the 
  Lamellibranchiata, 
  of 
  which 
  25 
  are 
  com- 
  

   mon, 
  only 
  20 
  species 
  out 
  of 
  1827 
  passed 
  to 
  the 
  Inferior 
  Oolite, 
  or 
  

   in 
  all 
  only 
  33 
  genera 
  and 
  45 
  species 
  of 
  all 
  groups 
  passed 
  to 
  the 
  

   Inferior 
  Oolite. 
  They 
  are 
  Annelida 
  §, 
  Brachiopoda 
  f 
  , 
  Monomyaria 
  

   ! 
  8 
  3, 
  Dimyaria 
  \\, 
  Gasteropoda 
  |, 
  and 
  Ammonites 
  \. 
  No 
  more 
  com- 
  

   plete 
  palaeontological 
  change 
  occurs 
  throughout 
  the 
  British 
  rocks 
  in 
  

   one 
  great 
  conformable 
  group. 
  The 
  result 
  of 
  the 
  analysis 
  of 
  every 
  

   thing 
  known 
  in 
  the 
  Lias, 
  and 
  the 
  community 
  of 
  all 
  species 
  with 
  

   the 
  rocks 
  above 
  is 
  expressed 
  in 
  the 
  following 
  Table 
  (XXV.), 
  which 
  

   shows 
  the 
  number 
  of 
  species 
  that 
  pass 
  from 
  the 
  Lias 
  to 
  the 
  higher 
  

   divisions 
  of 
  the 
  Jurassic 
  rocks. 
  

  

  * 
  Consult 
  the 
  works 
  of 
  Studer, 
  Suess, 
  Waagen, 
  Von 
  Hauer, 
  Keynes, 
  

   Quenstedt, 
  Oppel, 
  Dumortier, 
  Hart, 
  Barrois, 
  &c, 
  Wright, 
  Judd, 
  Tate 
  and 
  

   Blake, 
  and 
  many 
  others. 
  

  

  