﻿156 
  T. 
  F. 
  JAMIES0N 
  ON 
  THE 
  CRAG-SHELL 
  

  

  Mr. 
  S. 
  Y. 
  Wood, 
  informs 
  me 
  that 
  the 
  large 
  Pectunculus 
  "di- 
  

   stinctly 
  dies 
  out 
  as 
  we 
  ascend 
  the 
  Crag 
  series, 
  swarming 
  in 
  the 
  

   Coralline 
  Crag 
  and 
  in 
  the 
  older 
  part 
  of 
  the 
  Eed. 
  In 
  the 
  Norwich, 
  

   or 
  nuvio-marine, 
  Crag 
  only 
  one 
  small 
  specimen 
  has 
  ever 
  been 
  said 
  to 
  

   have 
  occurred 
  ; 
  and 
  in 
  the 
  Chillesford 
  shell-bed, 
  which 
  is 
  the 
  sand 
  

   immediately 
  underlying 
  the 
  Chillesford 
  clay, 
  only 
  one 
  small 
  much- 
  

   worn 
  valve 
  has 
  ever 
  occurred, 
  though 
  these 
  deposits 
  have 
  been 
  most 
  

   assiduously 
  hunted 
  by 
  various 
  collectors. 
  In 
  the 
  lower 
  glacial 
  we 
  

   have 
  never 
  seen 
  a 
  trace 
  of 
  it. 
  On 
  the 
  other 
  hand 
  it 
  is 
  very 
  common 
  

   in 
  the 
  middle 
  glacial, 
  but 
  always 
  small, 
  the 
  larger 
  specimens 
  frag- 
  

   mentary, 
  but 
  the 
  fry 
  quite 
  unworn 
  and 
  perfect." 
  Mr. 
  S. 
  Y. 
  Wood, 
  

   also 
  conments 
  on 
  the 
  absence 
  of 
  Tellina 
  obliqua 
  from 
  among 
  the 
  

   Slains 
  specimens. 
  This 
  shell, 
  he 
  says, 
  " 
  swarms 
  in 
  all 
  the 
  newer 
  

   beds 
  of 
  the 
  Crag 
  and 
  in 
  the 
  Lower 
  Glacial, 
  and 
  occurs, 
  although 
  not 
  

   common, 
  in 
  the 
  Middle 
  Glacial; 
  but 
  it 
  is 
  unique 
  at 
  Bridlington. 
  T. 
  

   prcetenuis 
  is 
  also 
  a 
  swarming 
  Crag 
  shell, 
  but 
  not 
  common 
  in 
  the 
  

   Lower 
  Glacial, 
  and 
  not 
  yet 
  met 
  with 
  in 
  the 
  Middle 
  Glacial 
  or 
  at 
  

   Bridlington. 
  The 
  newer 
  beds 
  of 
  the 
  Eed 
  Crag, 
  the 
  Norwich 
  Crag, 
  

   and 
  the 
  Chillesford 
  beds 
  are 
  almost 
  made 
  up 
  of 
  these 
  two 
  Tellens 
  ; 
  

   and 
  it 
  is 
  very 
  odd 
  that 
  in 
  such 
  a 
  case 
  no 
  trace 
  of 
  them 
  should 
  occur 
  

   with 
  you." 
  {Letter 
  of 
  date 
  25 
  March, 
  1870.) 
  

  

  Pecten 
  maximus, 
  P. 
  opercularis, 
  Venus 
  casina, 
  and 
  Venus 
  (Artemis) 
  

   lincta 
  appear 
  in 
  some 
  lists 
  as 
  Scotch 
  Glacial 
  species 
  ; 
  but 
  there 
  is 
  

   great 
  doubt 
  as 
  to 
  the 
  correctness 
  of 
  this. 
  The 
  careful 
  researches 
  of 
  

   Messrs. 
  Eobertson 
  and 
  Crosskey 
  would 
  seem 
  to 
  show 
  that 
  they 
  do 
  

   not 
  occur 
  in 
  the 
  true 
  glacial 
  beds 
  of 
  Scotland. 
  

  

  Hinge-fragments 
  of 
  Astarte 
  are 
  common 
  in 
  the 
  Slains 
  gravel, 
  and 
  

   appear 
  to 
  represent 
  more 
  than 
  one 
  species 
  ; 
  but 
  they 
  are 
  too 
  worn 
  

   and 
  imperfect 
  for 
  satisfactory 
  determination. 
  I 
  have 
  several 
  pieces 
  

   of 
  Fusus 
  contrarius, 
  which 
  seems 
  to 
  have 
  been 
  more 
  common 
  

   than 
  the 
  dextral 
  variety, 
  and 
  also 
  a 
  few 
  of 
  Nassa 
  reticosa; 
  of 
  

   Nucula 
  Cobboldice 
  only 
  one 
  hinge-fragment, 
  but 
  showing 
  traces 
  of 
  the 
  

   zigzag 
  markings 
  characteristic 
  of 
  this 
  species. 
  I 
  found 
  it 
  near 
  the 
  very 
  

   bottom 
  of 
  the 
  deep 
  mass 
  of 
  sand 
  in 
  the 
  coast-section 
  at 
  Collieston. 
  

   Of 
  Purpura 
  incrassata 
  I 
  have 
  three 
  specimens, 
  quite 
  characteristic, 
  

   and 
  two 
  of 
  them 
  nearly 
  complete. 
  Of 
  Trophon 
  costiferum 
  I 
  have 
  

   only 
  one 
  small 
  young 
  specimen, 
  nearly 
  complete, 
  but 
  much 
  worn. 
  

   Both 
  the 
  Messrs. 
  Wood 
  and 
  the 
  late 
  Dr. 
  S. 
  P. 
  Woodward, 
  who 
  also 
  

   saw 
  it, 
  think 
  it 
  probably 
  this 
  species. 
  

  

  Of 
  Turritella 
  incrassata 
  I 
  have 
  only 
  a 
  few 
  fragments 
  ; 
  but 
  the 
  

   Messrs. 
  Wood 
  pronounced 
  them 
  to 
  be 
  undoubtedly 
  this 
  shell. 
  Of 
  

   Voluta 
  Lamberti 
  I 
  have 
  only 
  one 
  clear 
  specimen, 
  which 
  consists 
  of 
  

   the 
  very 
  characteristic 
  columella 
  or 
  pillar 
  of 
  a 
  large-sized 
  individual, 
  

   much 
  worn, 
  but 
  quite 
  unmistakable 
  ; 
  I 
  found 
  it 
  in 
  the 
  gravel 
  of 
  the 
  

   Kippet 
  Hills, 
  near 
  the 
  Loch 
  of 
  Slains. 
  Fragments 
  of 
  Pectunculus 
  

   glycymeris 
  are 
  not 
  very 
  rare 
  : 
  and 
  most 
  of 
  them 
  indicate 
  a 
  large 
  size 
  

   of 
  shell, 
  such 
  as 
  occurs 
  in 
  the 
  Eed 
  and 
  Coralline 
  Crag. 
  

  

  Small 
  pieces 
  of 
  Pecten 
  are 
  very 
  common 
  ; 
  but 
  they 
  are 
  too 
  frag- 
  

   mentary 
  and 
  worn 
  for 
  satisfactory 
  identification 
  e 
  Most 
  of 
  them 
  

   seem 
  to 
  agree 
  with 
  P. 
  opercularis, 
  so 
  far 
  as 
  they 
  go. 
  

  

  