﻿162 
  E. 
  S. 
  Morse 
  — 
  Fossil 
  Shells 
  in 
  Boston 
  Basin. 
  

  

  is 
  discovered 
  that 
  there 
  are 
  two 
  distinct 
  deposits, 
  or 
  

   layers, 
  in 
  which 
  fossil 
  shells 
  are 
  found, 
  separated 
  by 
  a 
  

   few 
  inches 
  of 
  non-fossiliferons 
  material. 
  A 
  catalogue 
  of 
  

   the 
  species 
  of 
  shells 
  discovered 
  revealed 
  the 
  interesting 
  

   fact 
  that 
  the 
  lower 
  deposit 
  contained 
  shells 
  belonging 
  to 
  

   a 
  southern 
  fanna 
  while 
  the 
  npper 
  deposit 
  contained 
  

   shells 
  belonging 
  to 
  a 
  northern 
  fanna. 
  A 
  number 
  of 
  spe- 
  

   cies 
  are 
  identical 
  in 
  both 
  deposits. 
  Verrill 
  suggests 
  that 
  

   when 
  the 
  lower 
  fossiliferous 
  bed 
  was 
  deposited 
  a 
  shallow 
  

   bay 
  existed 
  at 
  this 
  place 
  from 
  which 
  the 
  outer 
  waters 
  

   were 
  excluded, 
  either 
  by 
  an 
  island 
  to 
  the 
  eastward, 
  or 
  

   else 
  by 
  a 
  southern 
  prolongation 
  of 
  Cape 
  Cod. 
  The 
  ex- 
  

   tensive 
  submerged 
  shoals 
  south 
  of 
  Cape 
  Cod 
  and 
  east 
  and 
  

   southeast 
  of 
  Nantucket 
  may 
  be 
  the 
  remains 
  of 
  such 
  land. 
  

   If 
  one 
  consults 
  a 
  chart 
  of 
  the 
  United 
  States 
  Coast 
  and 
  

   Geodetic 
  Survey 
  relating 
  to 
  the 
  waters 
  of 
  the 
  Nantucket 
  

   region 
  he 
  will 
  observe 
  a 
  number 
  of 
  shoals 
  parallel 
  to 
  

   Sankaty 
  Head, 
  known 
  a 
  hundred 
  years 
  ago 
  as 
  Old 
  Man, 
  

   Bat's 
  Rip, 
  Great 
  Rip, 
  Fishing 
  Rip 
  and 
  to 
  the 
  west 
  as 
  

   South 
  Shoal, 
  and 
  Fish 
  Rips, 
  and 
  running 
  west, 
  shallow 
  

   soundings 
  to 
  Gardiner's 
  Bay, 
  Long 
  Island 
  Sound. 
  Is 
  it 
  

   not 
  possible 
  that 
  these 
  various 
  shoals 
  indicate 
  a 
  termi- 
  

   nal 
  moraine, 
  like 
  that 
  of 
  Cape 
  Cod, 
  and 
  parallel 
  to 
  it, 
  but 
  

   worn 
  away 
  by 
  wind, 
  rain 
  and 
  ocean 
  currents, 
  leaving 
  the 
  

   shoals 
  and 
  shallow 
  soundings 
  above 
  referred 
  to 
  as 
  the 
  

   last 
  remains 
  of 
  the 
  barrier! 
  This 
  was 
  formed 
  before 
  

   Cape 
  Cod 
  existed, 
  and 
  before 
  this 
  earlier 
  barrier 
  was 
  

   made 
  southern 
  shells 
  extended 
  along 
  the 
  coast 
  as 
  already 
  

   described 
  in 
  this 
  paper, 
  and 
  this 
  accounted 
  for 
  the 
  

   southern 
  shells 
  found 
  in 
  the 
  lower 
  deposit. 
  After 
  the 
  

   first 
  terminal 
  moraine 
  was 
  formed 
  the 
  northern 
  mollus- 
  

   can 
  fauna 
  soon 
  established 
  itself 
  accounting 
  for 
  the 
  

   northern 
  shells 
  in 
  the 
  upper 
  deposit. 
  The 
  prompt 
  way 
  

   in 
  which 
  a 
  change 
  in 
  fauna 
  may 
  occur 
  is 
  illustrated 
  by 
  

   the 
  rapid 
  distribution 
  of 
  the 
  common 
  English 
  periwinkle, 
  

   Litorina 
  litorea, 
  which 
  was 
  found 
  in 
  the 
  Bay 
  of 
  Chaleur 
  

   in 
  the 
  early 
  years 
  of 
  the 
  last 
  century. 
  In 
  the 
  Catalogue 
  

   of 
  Marine 
  Invertebrata 
  of 
  Eastern 
  Canada, 
  by 
  J. 
  F. 
  

   "Whiteaves, 
  Geological 
  Survey 
  of 
  Canada, 
  1901, 
  it 
  is 
  

   stated 
  that 
  Sir 
  J. 
  W. 
  Dawson, 
  writing 
  in 
  1871, 
  says 
  of 
  

   Litorina 
  litorea: 
  "It 
  occurs 
  abundantly 
  and 
  of 
  large 
  size 
  

   off 
  different 
  parts 
  of 
  the 
  coast 
  of 
  Prince 
  Edward's 
  Island 
  

   as 
  it 
  does 
  also 
  on 
  the 
  opposite 
  coast 
  shore 
  of 
  Nova 
  Scotia 
  

   where 
  I 
  have 
  collected 
  the 
  species 
  more 
  than 
  forty 
  years 
  

  

  