﻿1864.] 
  BAWKINS 
  RH^ITIC 
  BEBS 
  ANB 
  WHITE 
  LIAS. 
  409 
  

  

  Conybeare 
  and 
  Phillips 
  give 
  the 
  thickness 
  of 
  the 
  White 
  Lias 
  at 
  

   Bath 
  Easton 
  as 
  10 
  feet, 
  at 
  Paulton 
  as 
  12 
  feet. 
  

  

  § 
  VI. 
  Summary. 
  

  

  The 
  four 
  points 
  that 
  I 
  have 
  striven 
  to 
  make 
  out 
  in 
  this 
  part 
  of 
  

   the 
  paper 
  are, 
  first, 
  the 
  true 
  position 
  of 
  the 
  White 
  Lias 
  immediately 
  

   upon 
  the 
  Avicula 
  contorta 
  series, 
  without 
  the 
  intercalation 
  of 
  any 
  

   Saurian 
  zone, 
  or 
  any 
  other 
  member 
  of 
  the 
  Ammonites 
  planorbis 
  

   group 
  ; 
  secondly, 
  its 
  isolation 
  from 
  the 
  Rhaetic 
  formation, 
  both 
  litholo- 
  

   gically 
  and 
  palaeontologically 
  ; 
  thirdly, 
  its 
  palaeontological 
  distinctness 
  

   from 
  the 
  Ammonites 
  planorbis 
  zone 
  ; 
  and 
  lastly, 
  the 
  downward 
  exten- 
  

   sion 
  of 
  the 
  Rhaetic 
  formation 
  below 
  the 
  bone-bed. 
  I 
  have 
  confined 
  

   myself 
  strictly 
  to 
  Somerset, 
  to 
  which 
  alone 
  my 
  observations 
  apply. 
  

   Their 
  application 
  to 
  other 
  districts 
  I 
  leave 
  to 
  the 
  greater 
  leisure 
  of 
  

   some 
  fellow- 
  worker 
  in 
  the 
  field 
  of 
  science. 
  

  

  Part 
  II. 
  On 
  the 
  Discovery 
  of 
  a 
  new 
  Fossil 
  Mammal 
  in 
  the 
  Grey 
  

   Marls 
  beneath 
  the 
  Bone-beb. 
  

  

  § 
  I. 
  Introduction. 
  

  

  So 
  far 
  back 
  as 
  1847 
  the 
  existence 
  of 
  a 
  Rhaetic 
  Mammal, 
  having 
  

   closer 
  affinities 
  with 
  the 
  Marsupials 
  than 
  with 
  any 
  other 
  order, 
  was 
  

   proved 
  by 
  the 
  discovery 
  of 
  Microlestes 
  in 
  the 
  bone-bed 
  of 
  Diegerloch*, 
  

   which 
  yielded 
  also 
  coprolites 
  and 
  Saurians. 
  Eleven 
  years 
  later, 
  in 
  

   1858, 
  Mr. 
  Charles 
  Moore, 
  F.G.S., 
  submitted 
  to 
  Professor 
  Owen 
  

   several 
  small 
  teeth 
  from 
  a 
  Rhaetic 
  breccia 
  that 
  filled 
  a 
  fissure 
  in 
  the 
  

   Mountain 
  Limestone, 
  near 
  Frome, 
  in 
  Somersetshire. 
  These 
  were 
  

   determined 
  to 
  belong 
  to 
  the 
  genus 
  Microlestes 
  of 
  Professor 
  Plienin- 
  

   ger, 
  and 
  to 
  be 
  most 
  closely 
  allied 
  to 
  the 
  Plagiaulax 
  found, 
  by 
  the 
  

   energy 
  of 
  Mr. 
  Beckles, 
  F.G.S., 
  at 
  Purbeck, 
  and 
  described 
  by 
  Dr. 
  

   Falconer, 
  F.R.S., 
  in 
  the 
  Journal 
  of 
  the 
  Society. 
  In 
  the 
  year 
  1861 
  

  

  1 
  had 
  the 
  good 
  fortune 
  to 
  discover 
  the 
  traces 
  of 
  a 
  Rhaetic 
  Mammal 
  

   on 
  the 
  sea-shore 
  to 
  the 
  west 
  of 
  Watchet, 
  in 
  the 
  rocks 
  that 
  underlie 
  

   the 
  bone-bed. 
  

  

  § 
  II. 
  Position 
  of 
  the 
  Fossil. 
  

  

  The 
  hard 
  arenaceous 
  marlstones 
  (F 
  of 
  fig. 
  1 
  of 
  the 
  preceding 
  

   Part), 
  which 
  yielded 
  the 
  first 
  traces 
  of 
  life 
  in 
  the 
  passage 
  from 
  the 
  

   red 
  marls 
  upwards, 
  yielded 
  also 
  the 
  tooth 
  in 
  question. 
  I 
  chiselled 
  

   it 
  out 
  of 
  the 
  ripple-marked 
  surface 
  of 
  a 
  reef 
  which 
  the 
  sea 
  had 
  freed 
  

   from 
  the 
  deposits 
  above, 
  and 
  out 
  of 
  which 
  also 
  were 
  obtained 
  teeth 
  

   of 
  Acrodus 
  minimus 
  and 
  Sargodon 
  Tomicus, 
  scales 
  of 
  Gyrolepis 
  

   Alberti 
  and 
  G. 
  tenuistriatus, 
  a 
  hollow 
  compact 
  Pterodactylian 
  bone, 
  a 
  

   portion 
  of 
  the 
  pen 
  of 
  Beloteuihis 
  or 
  Geoteuthis, 
  a 
  small 
  undetermined 
  

   amphicoelian 
  vertebra, 
  and 
  a 
  few 
  fragments 
  of 
  wood 
  and 
  of 
  Pecten 
  

   Valoniensis. 
  The 
  fissile 
  many-laminated 
  stone 
  did 
  not 
  admit 
  of 
  my 
  

   separating 
  the 
  layer 
  in 
  which 
  the 
  fossil 
  tooth 
  occurred 
  from 
  the 
  rest 
  

   of 
  the 
  laminae 
  that 
  make 
  up 
  the 
  mass 
  of 
  G. 
  Its 
  exact 
  position 
  was 
  

  

  2 
  feet 
  6 
  inches 
  below 
  the 
  lower 
  boundary 
  of 
  H 
  (fig. 
  1), 
  and 
  10 
  feet 
  

   6 
  inches 
  below 
  the 
  bone-bed. 
  Having 
  been 
  found 
  at 
  a 
  lower 
  horizon, 
  

  

  * 
  Jahreshefte 
  Wiirtemberg, 
  1847-48, 
  p. 
  164. 
  

  

  