﻿MAR 
  2 
  . 
  182i 
  

  

  THE 
  

  

  AMERICAN 
  JOURNAL 
  OF 
  SCIENCE 
  

  

  [FOURTH 
  SERIES.] 
  

  

  Art. 
  X. 
  — 
  On 
  Certain 
  Fossil 
  Shells 
  in 
  the 
  Bowlder 
  Clay 
  

   of 
  Boston 
  Basin; 
  by 
  Edward 
  S. 
  Morse. 
  

  

  The 
  numerous 
  deposits 
  of 
  bowlder 
  clay, 
  or 
  till, 
  that 
  

   compose 
  many 
  of 
  the 
  islands 
  in 
  Boston 
  Bay 
  and 
  head- 
  

   lands 
  along 
  the 
  coast, 
  notably 
  Point 
  Shirley 
  and 
  Hull, 
  

   have 
  been 
  minutely 
  studied 
  by 
  Crosby, 
  Ballard, 
  Upham 
  

   and 
  others. 
  In 
  these 
  indurated 
  clay 
  deposits 
  fragments 
  

   of 
  many 
  species 
  of 
  marine 
  shells 
  are 
  found. 
  In 
  pre-gla- 
  

   cial 
  days 
  the 
  region 
  known 
  as 
  Boston 
  Basin, 
  including 
  

   Cambridge 
  and 
  adjacent 
  territory 
  and 
  extending 
  back 
  to 
  

   the 
  Belmont 
  Hills, 
  was 
  submerged 
  by 
  the 
  sea 
  and 
  formed 
  

   a 
  large 
  shallow 
  bay, 
  or 
  inlet, 
  in 
  which 
  various 
  species 
  of 
  

   mollusks, 
  particularly 
  the 
  so-called 
  Venus 
  mercenaria, 
  

   thrived 
  under 
  the 
  most 
  favorable 
  conditions 
  for 
  growth 
  

   and 
  multiplication. 
  When 
  the 
  great 
  ice-field 
  advanced 
  

   from 
  the 
  north 
  it 
  scooped 
  up 
  the 
  clay 
  bottom 
  of 
  Boston 
  

   Basin 
  and 
  with 
  its 
  own 
  detritus 
  of 
  sand 
  and 
  bowlders 
  

   augmented 
  the 
  terminal 
  moraine 
  as 
  it 
  moved 
  southward. 
  

   It 
  not 
  only 
  pushed 
  these 
  masses 
  of 
  clay 
  ahead 
  but 
  rode 
  

   over 
  them 
  and 
  crushed 
  by 
  its 
  enormous 
  weight 
  the 
  shells 
  

   contained 
  in 
  them. 
  The 
  larger 
  shells, 
  recognized 
  as 
  

   Venus 
  mercenaria, 
  are 
  in 
  all 
  cases 
  broken 
  into 
  fragments 
  

   and 
  these 
  fragments 
  of 
  various 
  sizes, 
  rarely 
  over 
  an 
  inch 
  

   in 
  length, 
  are 
  worn 
  and 
  their 
  broken 
  edges 
  rounded 
  by 
  

   the 
  kneading 
  action 
  of 
  the 
  ice 
  mass. 
  In 
  vol. 
  48 
  (pp. 
  486- 
  

   496, 
  1894) 
  of 
  this 
  Journal 
  is 
  a 
  paper 
  entitled 
  "Distri- 
  

   bution 
  and 
  Probable 
  Age 
  of 
  the 
  Fossil 
  Shells 
  in 
  the 
  

   Drumlins 
  of 
  the 
  Boston 
  Basin, 
  by 
  W. 
  0. 
  Crosby 
  and 
  H. 
  0. 
  

   Ballard.' 
  ' 
  In 
  this 
  communication 
  a 
  map 
  is 
  given 
  of 
  the 
  

   Boston 
  Basin 
  on 
  which 
  is 
  indicated 
  by 
  numbers 
  the 
  

   islands 
  and 
  regions 
  on 
  the 
  main 
  land 
  where 
  these 
  deposits 
  

  

  Am. 
  Jour. 
  Sci.— 
  Fourth 
  Series, 
  Vol. 
  XLIX, 
  No. 
  291.— 
  March, 
  1920. 
  

   12 
  

  

  