﻿PROF. 
  C. 
  LAPWORTH 
  OX 
  THE 
  GIRVAN 
  SUCCESSION. 
  665 
  

  

  also 
  in 
  our 
  English 
  rocks 
  of 
  that 
  age 
  ; 
  and 
  some 
  more 
  have 
  been 
  

   found 
  in 
  Peeblesshire, 
  the 
  Lead-Hill 
  district, 
  and 
  in 
  some 
  other 
  

   places 
  in 
  Scotland, 
  which 
  will 
  swell 
  out 
  the 
  list 
  of 
  Scottish 
  Caradoc 
  

   forms. 
  Endeavouring 
  to 
  ascertain, 
  as 
  nearly 
  as 
  possible, 
  how 
  many 
  

   species 
  of 
  Caradoc 
  Brachiopoda 
  occur 
  in 
  the 
  Upper 
  Llandeilo 
  of 
  

   Scotland, 
  Dr. 
  Davidson 
  found 
  that 
  about 
  30, 
  or 
  a 
  little 
  more 
  than 
  

   half, 
  of 
  the 
  Upper 
  Llandeilo 
  species 
  passed 
  upwards 
  into 
  the 
  Caradoc, 
  

   or 
  were 
  common 
  to 
  both 
  periods. 
  

  

  With 
  respect 
  to 
  the 
  Llandovery, 
  which 
  Prof. 
  Lapworth 
  divides 
  

   into 
  Lower, 
  Middle, 
  and 
  Upper, 
  he 
  found 
  15 
  species 
  in 
  the 
  lower 
  

   division, 
  29 
  in 
  the 
  middle, 
  and 
  34 
  in 
  the 
  upper. 
  Of 
  these, 
  6 
  are 
  

   common 
  to 
  the 
  three 
  divisions, 
  14 
  to 
  the 
  middle 
  and 
  upper 
  divisions, 
  

   10 
  pass 
  from 
  the 
  Caradoc 
  into 
  the 
  Llandovery, 
  and 
  4 
  species 
  only 
  

   seem 
  to 
  have 
  passed 
  upwards 
  through 
  the 
  whole 
  Girvan 
  series, 
  

   viz. 
  Ortliis 
  calligramma, 
  0. 
  elegant 
  via, 
  Stropliomena 
  rliomboiclalis. 
  

   and 
  S. 
  Gorrugatella. 
  Thirty 
  of 
  the 
  Llandovery 
  species 
  occur 
  like- 
  

   wise 
  in 
  the 
  Wenlock 
  and 
  Ludlow 
  rocks. 
  There 
  is 
  therefore 
  a 
  very 
  

   marked 
  difference 
  between 
  the 
  species 
  of 
  Brachiopoda 
  that 
  charac- 
  

   terize 
  the 
  Upper 
  and 
  Lower 
  Silurian 
  rocks 
  of 
  Great 
  Britain. 
  

  

  Dr. 
  Hicks 
  said 
  the 
  paper 
  showed 
  how 
  we 
  were 
  gradually 
  being- 
  

   able 
  to 
  correlate 
  the 
  various 
  districts 
  of 
  the 
  Lower 
  Palaeozoic 
  rocks, 
  

   and 
  arriving 
  at 
  a 
  tolerably 
  universal 
  order 
  in 
  the 
  succession. 
  It 
  

   was 
  impossible 
  to 
  touch 
  upon 
  all 
  the 
  important 
  questions 
  raised 
  by 
  

   this 
  paper. 
  Among 
  them 
  he 
  would, 
  however, 
  notice 
  one 
  or 
  two. 
  The 
  

   paper 
  showed 
  that 
  in 
  one 
  direction 
  there 
  were 
  shore-lines, 
  and 
  in 
  

   another 
  there 
  were 
  deeper 
  waters 
  — 
  a 
  point 
  of 
  great 
  importance 
  in 
  

   physical 
  geology. 
  He 
  also 
  noticed 
  in 
  Prof. 
  Lapwortlfs 
  map, 
  in 
  one 
  

   corner, 
  an 
  area 
  of 
  metamorphic 
  rocks 
  overlain 
  by 
  conglomerates, 
  

   and 
  probably 
  of 
  Precambrian 
  age. 
  This 
  would 
  have 
  an 
  important 
  

   bearing 
  on 
  the 
  question 
  of 
  the 
  age 
  of 
  the 
  beds 
  in 
  the 
  north 
  of 
  a 
  

   similar 
  character, 
  but 
  supposed 
  by 
  Murchison 
  and 
  the 
  Survey 
  to 
  be 
  

   of 
  Silurian 
  age. 
  Here 
  also 
  we 
  find 
  the 
  newer 
  beds, 
  as 
  there, 
  fre- 
  

   quently 
  faulted 
  down 
  among 
  the 
  older 
  ones. 
  We 
  were 
  greatly 
  in- 
  

   debted 
  to 
  Prof. 
  Lapworth 
  for 
  the 
  admirable 
  work 
  he 
  had 
  done. 
  

  

  Prof. 
  Hughes 
  agreed 
  with 
  the 
  conclusions 
  of 
  Prof. 
  Lapworth, 
  

   and 
  pointed 
  out 
  that 
  in 
  Wales 
  and 
  England 
  we 
  had 
  the 
  same 
  order 
  

   of 
  succession 
  of 
  the 
  life-zones 
  so 
  far 
  as 
  they 
  had 
  been 
  worked 
  out. 
  

   In 
  Xorth 
  Wales 
  the 
  Llandeilo 
  beds 
  were 
  not 
  well 
  defined, 
  being 
  near 
  

   the 
  volcanic 
  centre 
  ; 
  in 
  South 
  Wales 
  the)- 
  were 
  more 
  fossiliferous, 
  

   but 
  were 
  soon 
  overlapped. 
  The 
  great 
  difficulty 
  in 
  correlation 
  was 
  

   in 
  the 
  May-Hill 
  series 
  (Upper 
  and 
  Lower 
  Llandovery), 
  in 
  which 
  

   we 
  had 
  variable 
  basement 
  beds, 
  indicating 
  the 
  submergence 
  of 
  an 
  

   irregular 
  land 
  surface. 
  At 
  Llandovery 
  there 
  was 
  a 
  great 
  thickness 
  of 
  

   both 
  Upper 
  and 
  Lower 
  divisions, 
  with 
  the 
  zone 
  of 
  Strickland 
  inia 
  lens 
  

   and 
  Meristella 
  crassa 
  in 
  the 
  Lower, 
  and 
  of 
  Pcntamerus 
  oblongusm 
  the 
  

   Upper. 
  On 
  the 
  west 
  flanks 
  of 
  the 
  Malvern 
  range, 
  Avithin 
  the 
  area 
  

   mapped 
  as 
  Hollybush 
  Sandstone, 
  he 
  had 
  found 
  May-Hill 
  beds 
  below 
  

   the 
  zone 
  of 
  P. 
  oblotigus. 
  In 
  North 
  Wales 
  and 
  the 
  Lake-district 
  

   there 
  is 
  no 
  clear 
  equivalent 
  of 
  the 
  Upper 
  May-Hill 
  ; 
  but 
  a 
  variable 
  

   basement 
  scries 
  can 
  be 
  traced 
  having 
  palrcontologieal 
  affinities 
  with 
  

  

  Q. 
  J. 
  G. 
  S. 
  No. 
  152. 
  2 
  t 
  

  

  