﻿138 
  TKOCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  indeed, 
  classical 
  localities 
  for 
  clear 
  demonstration 
  of 
  the 
  succession 
  of 
  

   the 
  Ammonite 
  zones 
  of 
  the 
  entire 
  Lias 
  formation. 
  

  

  " 
  This 
  coast 
  section 
  may 
  be 
  said 
  to 
  be 
  complete 
  from 
  the 
  great 
  

   arenaceous 
  deposit 
  of 
  Upper 
  Lias 
  sand, 
  containing 
  Harpoceras 
  opali- 
  

   num, 
  with 
  each 
  succeeding 
  zone 
  of 
  the 
  Upper, 
  Middle, 
  and 
  Lower 
  

   Lias, 
  down 
  to 
  JEgoceras 
  planorhis, 
  and 
  its 
  Ostrea 
  series 
  [O. 
  liassica] 
  

   resting 
  on 
  the 
  Avicula-contorta 
  beds 
  of 
  the 
  Trias'' 
  near 
  Axmouth 
  *. 
  

  

  lihcetic 
  or 
  Avicula-contorta 
  Beds, 
  Portlock, 
  1843. 
  

  

  Kossener 
  Schichten, 
  Von 
  Hauer, 
  1853. 
  

  

  Oberes 
  St. 
  Cassian, 
  Escher, 
  1853. 
  

  

  Gervillien- 
  (Kossener) 
  Schichten, 
  Gilmbel, 
  1856. 
  

  

  Die 
  Zone 
  der 
  Avicula 
  contorta, 
  Oppel, 
  1859. 
  

  

  Infra-Lias 
  du 
  departement 
  de 
  la 
  Cote 
  d'Or, 
  Jules 
  Martin, 
  1860. 
  

  

  These 
  and 
  numerous 
  other 
  names 
  constitute 
  the 
  synonymy 
  of 
  the 
  

   Avicula-contorta 
  zone, 
  a 
  name 
  given 
  by 
  Col. 
  Portlock 
  in 
  1843 
  to 
  

   beds 
  in 
  the 
  N. 
  of 
  Ireland 
  containing 
  the 
  shells 
  Avicula 
  contorta 
  and 
  

   Pecten 
  valoniensis. 
  This 
  series 
  was 
  then 
  believed 
  to 
  belong 
  to 
  the 
  

   Lower 
  Lias, 
  and 
  for 
  many 
  years 
  this 
  view 
  was 
  held; 
  but 
  the 
  progress 
  

   of 
  research 
  into 
  the 
  history 
  and 
  structure 
  of 
  the 
  lihsetian 
  Alps 
  and 
  

   their 
  palaeontological 
  contents 
  resulted 
  in 
  clearly 
  determining 
  that 
  

   the 
  fauna 
  of 
  the 
  Avicula-contorta 
  or 
  Ehaetic 
  beds 
  belonged 
  to 
  the 
  

   Triassic 
  rather 
  than 
  to 
  the 
  Liassic 
  group, 
  especially 
  as 
  exemplified 
  by 
  

   the 
  Pishes 
  and 
  Rcptilia 
  ; 
  and 
  there 
  cannot 
  be 
  any 
  doubt 
  that 
  the 
  

   fauna 
  of 
  the 
  Avicula-contorta 
  zone 
  has 
  closer 
  affinities 
  with 
  that 
  

   of 
  the 
  Kossener 
  Schichten 
  of 
  the 
  Tyrol 
  and 
  the 
  Upper 
  St.- 
  Cassian 
  

   beds 
  of 
  Germany 
  (Escher) 
  than 
  with 
  the 
  Lias, 
  from 
  the 
  fact 
  that 
  

   most 
  of 
  the 
  species 
  found 
  in 
  the 
  Khaetic 
  beds 
  do 
  not 
  pass 
  into 
  the 
  

   Lower 
  Lias. 
  The 
  chief 
  species 
  of 
  Mollusca 
  are 
  Cardiam 
  rhceticum, 
  

   Pecten 
  valoniensis, 
  Neoscliizodus, 
  Pleuropliorus, 
  Avicula 
  contorta, 
  

   and 
  Schizodus 
  angulatus 
  (Myophoria). 
  Fishes 
  : 
  Nemacanihus, 
  Acro- 
  

   lepis, 
  Saryodon, 
  Saurichthys, 
  Gyrolepis, 
  Ceratodus, 
  &c. 
  The 
  Rep- 
  

   tilia 
  of 
  the 
  genera 
  Ichthyosaurus 
  and 
  Plesiosaurus 
  are 
  here 
  first 
  

   known, 
  but 
  with 
  species 
  differing 
  from 
  those 
  of 
  the 
  Lower 
  Lias. 
  

   The 
  earliest 
  mammal 
  known 
  (Microlestes 
  antiquvs) 
  occurs 
  in 
  the 
  

   Rhaetic 
  beds 
  of 
  this 
  country 
  as 
  well 
  as 
  in 
  those 
  at 
  Dierloch, 
  in 
  

   Wurttemberg. 
  From 
  Eedcar 
  in 
  Yorkshire 
  to 
  Lyme 
  Regis 
  in 
  Dor- 
  

   setshire 
  we 
  obtain 
  the 
  Avicula-contorta 
  beds 
  wherever 
  the 
  junc- 
  

   tion 
  of 
  the 
  Trias 
  and 
  Lias 
  is 
  revealed 
  ; 
  and 
  they 
  retain 
  their 
  physical 
  

   and 
  paheontological 
  characters 
  throughout, 
  consisting 
  of 
  black 
  

   pyritous 
  shales 
  and 
  thin 
  impure 
  limestones 
  crowded 
  with 
  ill-pre- 
  

   served 
  shells. 
  

  

  On 
  the 
  continent 
  of 
  Europe 
  this 
  Rhsetic 
  or 
  Avicula-contorta 
  zone 
  

   has 
  also 
  a 
  most 
  extensive 
  geographical 
  range. 
  Its 
  deposits 
  are 
  met 
  

   with 
  in 
  Germany, 
  Switzerland, 
  France, 
  Hungary, 
  and 
  as 
  far 
  north 
  as 
  

   Sweden. 
  "We 
  find 
  them 
  in 
  Wiirttemberg, 
  near 
  Tubingen, 
  Stuttgart, 
  

   and 
  Gottingen 
  ; 
  in 
  Baden, 
  at 
  Bamberg 
  and 
  Baireuth 
  ; 
  near 
  Bruns- 
  

  

  * 
  Dr. 
  Wright, 
  Palseoiitographical 
  Soc. 
  vol. 
  xxxii., 
  Monogr. 
  Lias 
  Ammonites, 
  

   p. 
  2 
  (1878). 
  

  

  