﻿34 
  I. 
  MELLAKD 
  READE 
  ON 
  THE 
  

  

  Boulder-clays, 
  as 
  well 
  as 
  the 
  one 
  found 
  most 
  frequently 
  perfect, 
  is 
  

   Turritella 
  terebra. 
  Tellina 
  balihica 
  comes 
  next 
  in 
  the 
  scale 
  of 
  fre- 
  

   quency, 
  but 
  is 
  seldom 
  found 
  perfect. 
  Cardium 
  eclule, 
  C. 
  echinatum, 
  

   and 
  Cyprina 
  islandica, 
  always 
  found 
  in 
  fragments, 
  follow 
  in 
  the 
  

   order 
  given 
  ; 
  but 
  the 
  typical 
  fossil, 
  the 
  representative 
  of 
  the 
  climatic 
  

   conditions 
  prevailing 
  at 
  the 
  time 
  the 
  clays 
  were 
  laid 
  down, 
  is 
  un- 
  

   doubtedly 
  in 
  my 
  opinion 
  Astarte 
  borealis. 
  Though 
  not 
  the 
  most 
  fre- 
  

   quent, 
  it 
  is 
  a 
  common 
  fossil 
  ; 
  «. 
  and 
  I 
  have 
  found 
  it 
  in 
  all 
  the 
  localities 
  

   mentioned 
  in 
  the 
  list, 
  as 
  well 
  as 
  in 
  other 
  places 
  unrecorded. 
  It 
  has 
  

   also 
  been 
  found 
  in 
  the 
  same 
  series 
  of 
  clays 
  at 
  Blackpool, 
  Warrington, 
  

   Chester, 
  and 
  other 
  places, 
  by 
  independent 
  observers. 
  Unlike 
  Leda 
  

   pemula, 
  which, 
  though 
  occurring 
  in 
  the 
  same 
  clays, 
  is 
  rare, 
  or 
  Sa.vi- 
  

   cava 
  norvegica, 
  which 
  is 
  represented 
  only 
  by 
  two 
  fragments, 
  Astarte 
  

   borealis 
  may 
  safely 
  be 
  taken 
  as 
  indicative 
  of 
  the 
  then 
  condition 
  of 
  the 
  

   British 
  seas. 
  According 
  to 
  Mr. 
  Gwyn 
  Jeffreys, 
  " 
  the 
  most 
  southern 
  

   known 
  limit 
  of 
  its 
  habitation 
  is 
  Kiel 
  Bay 
  in 
  the 
  Baltic." 
  Astarte 
  

   compressa, 
  A. 
  elliptica, 
  and 
  Trophon 
  truncatus, 
  also 
  fossils 
  of 
  the 
  clay, 
  

   though 
  still 
  existing 
  in 
  the 
  British 
  seas, 
  are 
  confined 
  to 
  the 
  northern 
  

   portion 
  of 
  them, 
  and 
  increase 
  in 
  number 
  of 
  individuals 
  as 
  theyapproach 
  

   the 
  Arctic 
  circle. 
  A 
  reference 
  to 
  the 
  list 
  will 
  also 
  show 
  that 
  twelve 
  

   of 
  the 
  remaining 
  species 
  are 
  northern 
  and 
  Celtic 
  shells, 
  scarcely 
  

   ranging 
  south 
  of 
  the 
  British 
  seas. 
  Twenty-one 
  range 
  far 
  south 
  into 
  

   the. 
  Lusitanian 
  and 
  Mediterranean 
  regions, 
  but 
  are 
  most 
  prolific 
  in 
  

   the 
  Celtic 
  and 
  northern 
  seas 
  ; 
  while 
  Venus 
  chione 
  (several 
  well-marked 
  

   hinge-fragments 
  of 
  which 
  as 
  well 
  as 
  other 
  fragments 
  I 
  found 
  at 
  Edge- 
  

   hill), 
  Dentalium 
  tarentinum, 
  and 
  Cardium 
  tuberculatum 
  (only 
  single 
  

   fragments 
  of 
  which 
  occurred 
  to 
  me) 
  are 
  southern 
  shells. 
  

  

  Though 
  all, 
  with 
  the 
  exception 
  of 
  Astarte 
  borealis, 
  Leda 
  pemula, 
  

   and 
  Saxicava 
  norvegica, 
  may 
  be 
  described 
  as 
  Irish-Sea 
  shells, 
  yet, 
  

   if 
  we 
  make 
  a 
  fair 
  comparison, 
  we 
  shall 
  find 
  that 
  the 
  Boulder-clay 
  

   assemblage 
  possesses 
  a 
  more 
  northern 
  facies 
  than 
  the 
  present 
  fauna 
  

   of 
  the 
  British 
  seas. 
  If 
  I 
  may 
  so 
  express 
  it, 
  the 
  area 
  of 
  the 
  Boulder- 
  

   clay 
  fauna 
  and 
  that 
  of 
  the 
  present 
  British 
  seas 
  Overlap; 
  but 
  their 
  centres 
  

   are 
  considerably 
  apart, 
  that 
  of 
  the 
  former 
  being 
  in 
  a 
  higher 
  latitude. 
  

   To 
  assist 
  in 
  the 
  illustration 
  of 
  this 
  idea, 
  I 
  have 
  given 
  a 
  column 
  showing 
  

   the 
  species 
  now 
  found 
  on 
  the 
  shore 
  between 
  Southport 
  and 
  Formby, 
  

   the 
  nearest 
  locality 
  for 
  comparison 
  ; 
  and 
  reference 
  to 
  it 
  will 
  show 
  that 
  

   the 
  most 
  characteristic 
  northern 
  forms 
  are 
  absent. 
  There 
  are 
  in 
  

   addition 
  also 
  many 
  Celtic 
  and 
  southern 
  forms 
  found 
  on 
  the 
  same 
  

   beach 
  which 
  are 
  absent 
  in 
  the 
  Boulder-clay. 
  

  

  The 
  presence 
  of 
  Venus 
  chione 
  in 
  the 
  low-level 
  Boulder-clays 
  as 
  well 
  

   as 
  in 
  the 
  Macclesfield 
  drift 
  where 
  it 
  was 
  first 
  discovered 
  by 
  Mr. 
  Dar- 
  

   bishire, 
  is 
  certainly 
  a 
  remarkable 
  fact 
  ; 
  but 
  it 
  is 
  not 
  an 
  isolated 
  one 
  ; 
  

   for 
  Cardium 
  aculeatum 
  and 
  C. 
  pygmceum, 
  both 
  Lusitanian 
  forms, 
  are 
  

   found 
  in 
  the 
  Scotch 
  drift 
  ; 
  and 
  in 
  the 
  Irish 
  drift 
  southern 
  forms 
  also 
  

  

  weight 
  of 
  fragments, 
  and 
  has 
  assisted 
  me 
  in 
  various 
  ways. 
  To 
  Mr. 
  Gwyn 
  Jeffreys 
  

   I 
  owe 
  the 
  identification 
  of 
  some 
  of 
  the 
  more 
  doubtful 
  species, 
  and 
  a 
  revision 
  of 
  

   my 
  list. 
  

  

  