﻿15S 
  E. 
  S. 
  Morse 
  — 
  Fossil 
  Shells 
  in 
  Boston 
  Basin. 
  

  

  are 
  found. 
  Some 
  of 
  these 
  masses 
  of 
  clay 
  have 
  been 
  

   pushed 
  up 
  by 
  the 
  ice-field 
  to 
  the 
  height 
  of 
  a 
  hundred 
  feet 
  

   or 
  more. 
  A 
  list 
  is 
  given 
  of 
  the 
  species 
  of 
  mollusks 
  thus 
  

   far 
  identified. 
  These 
  number 
  fifty 
  species 
  and 
  most 
  of 
  

   them 
  are 
  found 
  living 
  to-day 
  in 
  Massachusetts 
  Bay. 
  In 
  

   the 
  list, 
  however, 
  are 
  a 
  number 
  of 
  species 
  which 
  belong 
  

   to 
  the 
  molluscan 
  fauna 
  south 
  of 
  Cape 
  Cod. 
  These 
  are 
  

   Ostrea 
  borealis, 
  Venus 
  mercenaria, 
  and 
  Pecten 
  ir 
  radians. 
  

   The 
  Ostrea 
  and 
  Venus 
  are 
  still 
  found 
  living 
  in 
  certain 
  

   restricted 
  localities 
  north 
  of 
  Cape 
  Cod. 
  Some 
  hundreds 
  

   of 
  years 
  ago 
  these 
  three 
  species 
  must 
  have 
  been 
  abundant 
  

   and 
  more 
  widely 
  distributed, 
  as 
  the 
  Indian 
  shellheaps 
  

   along 
  the 
  coast, 
  north 
  of 
  Cape 
  Cod, 
  reveal 
  the 
  presence 
  

   of 
  the 
  shells 
  of 
  these 
  species 
  in 
  numbers. 
  Dredgings 
  in 
  

   Portland 
  Harbor 
  for 
  the 
  purpose 
  of 
  deepening 
  the 
  chan- 
  

   nel 
  exposed 
  a 
  large 
  bed 
  of 
  Pecten 
  irradians 
  and 
  associ- 
  

   ated 
  with 
  these 
  shells 
  was 
  found 
  Turbinella 
  interrupta, 
  

   a 
  shell 
  restricted 
  to 
  a 
  few 
  localities 
  north 
  of 
  Cape 
  Cod, 
  

   but 
  common 
  south 
  of 
  it. 
  

  

  In 
  these 
  clay 
  deposits 
  of 
  Boston 
  Basin 
  are 
  found 
  spar- 
  

   ingly 
  two 
  species 
  of 
  Area, 
  A. 
  pexata 
  and 
  A. 
  transversa; 
  

   these 
  have 
  never 
  been 
  found 
  living 
  north 
  of 
  Cape 
  Cod, 
  nor 
  

   have 
  they 
  been 
  found 
  in 
  the 
  Indian 
  shellheaps 
  nor 
  in 
  the 
  

   dredgings 
  of 
  Portland 
  Harbor. 
  All 
  the 
  evidence 
  thus 
  

   far 
  cited 
  indicates 
  that 
  in 
  pre-giacial 
  times 
  the 
  waters 
  of 
  

   the 
  ocean 
  bordering 
  the 
  coast 
  had 
  a 
  far 
  higher 
  tempera- 
  

   ture 
  than 
  that 
  which 
  obtains 
  to-day. 
  Various 
  explana- 
  

   tions 
  have 
  been 
  given 
  as 
  to 
  the 
  cause 
  of 
  this 
  condition. 
  

   The 
  lower 
  temperature 
  of 
  Massachusetts 
  Bay 
  comes 
  from 
  

   a 
  northern 
  current 
  from 
  the 
  Gulf 
  of 
  Maine 
  sweeping 
  

   down 
  into 
  Massachusetts 
  Bay 
  bringing 
  with 
  it 
  a 
  northern 
  

   fauna, 
  while 
  a 
  southern 
  current 
  sweeping 
  up 
  from 
  the 
  

   south 
  brings 
  with 
  it 
  the 
  southern 
  shells 
  which 
  are 
  found 
  

   on 
  the 
  southern 
  shores 
  of 
  Cape 
  Cod. 
  Dr. 
  A. 
  A. 
  Gould, 
  

   in 
  his 
  Report 
  on 
  the 
  Invertebrate 
  Animals 
  of 
  Massachu- 
  

   setts, 
  published 
  by 
  the 
  State 
  in 
  1841, 
  writes 
  as 
  follows 
  

   (page 
  315), 
  in 
  regard 
  to 
  the 
  separation 
  of 
  the 
  northern 
  

   and 
  southern 
  fauna 
  by 
  Cape 
  Cod. 
  He 
  says 
  : 
  

  

  ' 
  ' 
  The 
  distribution 
  of 
  the 
  marine 
  shells 
  is 
  well 
  worthy 
  of 
  notice 
  

   as 
  a 
  geological 
  fact. 
  Cape 
  Cod, 
  the 
  right 
  arm 
  of 
  the 
  Common- 
  

   wealth, 
  reaches 
  out 
  into 
  the 
  ocean, 
  some 
  50 
  or 
  60 
  miles. 
  It 
  is 
  

   nowhere 
  many 
  miles 
  wide; 
  but 
  this 
  narrow 
  point 
  of 
  land 
  has 
  

   hitherto 
  proved 
  a 
  barrier 
  to 
  the 
  migrations 
  of 
  many 
  species 
  of 
  

   mollusca. 
  Several 
  genera 
  and 
  numerous 
  species, 
  which 
  are 
  

   separated 
  by 
  the 
  intervention 
  of 
  only 
  a 
  few 
  miles 
  of 
  land, 
  are 
  

  

  