﻿288 
  PROCKEDINGS 
  OK 
  THE 
  MALACOLOGICAL 
  SOCIEXr. 
  

  

  Scalpa, 
  and 
  Skye, 
  which 
  had 
  been 
  collected 
  by 
  Sir 
  Archibald 
  Geikie. 
  

   From 
  an 
  examination 
  of 
  these 
  specimens 
  he 
  found 
  it 
  possible 
  to 
  

   partially 
  zone 
  the 
  beds 
  of 
  that 
  region, 
  a 
  result 
  more 
  or 
  less 
  accom- 
  

   plished 
  from 
  a 
  comparison 
  with 
  the 
  faunas 
  characterizing 
  the 
  Liassic 
  

   subdivisions 
  of 
  Swabia 
  (Quenstedt), 
  Wiirteraberg 
  (Oppel), 
  France 
  

   (Orbigny), 
  and 
  Gloucestershire 
  (Wright). 
  

  

  Lower 
  Lias 
  beds 
  were 
  recognized 
  in 
  Skye, 
  not 
  by 
  Ammonite 
  

   remains, 
  but 
  by 
  the 
  presence 
  of 
  Cardinia 
  concinna, 
  J. 
  Sowerby, 
  

   a 
  species 
  characterizing 
  fairly 
  low 
  deposits 
  of 
  the 
  Lower 
  Lias 
  in 
  

   Wiirtemberg 
  and 
  France 
  ; 
  Ostrea 
  arietis, 
  Quenstedt, 
  was 
  also 
  

   determined 
  from 
  the 
  same 
  locality 
  and 
  beds. 
  

  

  The 
  better 
  preserved 
  shells, 
  however, 
  were 
  obtained 
  from 
  the 
  

   ' 
  Pabba 
  Shales 
  ' 
  and 
  regarded 
  as 
  of 
  Middle 
  Lias 
  age 
  — 
  

  

  Cephalopoda 
  . 
  . 
  Belenmites 
  elongatus, 
  paxillosus, 
  Ireviformis 
  ; 
  

   Ammonites 
  Jamesoni, 
  brevispina, 
  Davcei. 
  

  

  Gastropoda 
  . 
  . 
  . 
  Trochns 
  imhricatus. 
  

  

  Pelecypoda 
  . 
  . 
  . 
  Gryphcea 
  cymlium, 
  ohliquata 
  ; 
  Gervillia 
  Ilac- 
  

   cullochi 
  ; 
  Plicatula 
  spmosa 
  ; 
  Pecien 
  (equi- 
  

   valvis 
  ; 
  Inoceramus 
  ve>itricosns 
  ; 
  Limea 
  

   acuticosia 
  ; 
  Lima 
  Hermanni, 
  gigantea 
  ; 
  Pinna 
  

   folium 
  ; 
  Mytilus 
  cimeatus 
  ; 
  Unicardium 
  

   cardioides 
  ; 
  Pleuromya 
  unioides, 
  Scottica 
  ; 
  

   Pholadomya 
  ambigua. 
  

  

  In 
  1860 
  Dr. 
  Thomas 
  Wright^ 
  published 
  his 
  scheme 
  for 
  the 
  sub- 
  

   divisions 
  of 
  the 
  Lower 
  Lias 
  as 
  exhibited 
  in 
  the 
  South 
  of 
  England. 
  

   He 
  selected 
  six 
  species 
  of 
  Ammonites 
  as 
  his 
  guide-fossils, 
  and 
  adopted 
  

   Oppel's 
  view 
  in 
  considering 
  Ammonites 
  raricostattis 
  as 
  forming 
  the 
  

   topmost 
  zone 
  of 
  the 
  series 
  ; 
  in 
  descending 
  order 
  these 
  zones 
  were 
  as 
  

   follows 
  : 
  — 
  

  

  Zone 
  of 
  Ammonites 
  raricostatics. 
  

   ,, 
  A. 
  oxynotus. 
  

   ,, 
  A. 
  ohtusus. 
  

   ,, 
  A. 
  Tiirneri. 
  

   ,, 
  A. 
  BucJdandi. 
  

   ,, 
  A. 
  planorbis. 
  

  

  During 
  1875 
  Professor 
  Judd'^ 
  published 
  his 
  memoir 
  on 
  the 
  " 
  Geology 
  

   of 
  Eutlaud", 
  in 
  which 
  he 
  classified 
  into 
  zones 
  the 
  various 
  beds 
  of 
  the 
  

   Lias 
  of 
  that 
  district, 
  founded 
  on 
  species 
  of 
  Ammonites. 
  He 
  took 
  

   occasion 
  to 
  warn 
  the 
  student 
  against 
  placing 
  too 
  great 
  a 
  reliance 
  on 
  

   the 
  zonal 
  fossils, 
  because, 
  as 
  deposits 
  were 
  distributed 
  over 
  great 
  areas, 
  

   certain 
  gradual 
  changes 
  may 
  have 
  taken 
  place 
  in 
  their 
  faunas, 
  so 
  much 
  

   so 
  in 
  fact 
  that 
  the 
  index-species 
  observed 
  in 
  one 
  district 
  may 
  be 
  even 
  

   missing 
  from 
  the 
  same 
  stratum 
  when 
  occurring 
  in 
  another 
  locality. 
  

   Professor 
  Judd 
  concluded 
  from 
  this 
  that 
  zonal 
  species 
  are 
  not 
  

   uniformly 
  the 
  same 
  over 
  a 
  great 
  area, 
  although 
  the 
  general 
  assemblage 
  

   of 
  organisms 
  presents 
  a 
  similar 
  facies. 
  This 
  author's 
  divisions 
  of 
  the 
  

  

  ^ 
  Quart. 
  Journ. 
  Geol. 
  See, 
  vol. 
  xvi, 
  p. 
  374, 
  1860. 
  

   2 
  Mem. 
  Geol. 
  Surv. 
  England 
  and 
  Wales, 
  1875, 
  p. 
  89. 
  

  

  