﻿160 
  E. 
  S. 
  Morse 
  — 
  Fossil 
  Shells 
  in 
  Boston 
  Basin. 
  

  

  such 
  an 
  effect. 
  Certainly, 
  Bhabdonia 
  tenera 
  is 
  quite 
  unknown 
  

   in 
  any 
  other 
  spot 
  north 
  of 
  Cape 
  Cod, 
  the 
  nearest 
  locality 
  being 
  

   the 
  coast 
  near 
  Nantucket, 
  and 
  it 
  is 
  very 
  difficult 
  to 
  conceive 
  that 
  

   spores 
  of 
  that 
  delicate 
  species 
  would 
  survive 
  in 
  a 
  very 
  cold 
  cur- 
  

   rent, 
  which 
  not 
  only 
  must 
  carry 
  them 
  outside 
  of 
  Cape 
  Cod 
  and 
  

   across 
  Massachusetts 
  Bay, 
  but 
  also 
  around 
  to 
  the 
  sheltered 
  cove 
  

   at 
  the 
  point 
  where 
  Cape 
  Ann 
  joins 
  the 
  mainland 
  at 
  the 
  north. 
  

   If 
  we 
  compare 
  the 
  exceptional 
  case 
  of 
  Goose 
  Cove 
  in 
  the 
  north 
  

   with 
  Gay 
  Head 
  and 
  Montauk 
  in 
  the 
  south, 
  it 
  seems 
  to 
  be 
  the 
  

   rule 
  that 
  wherever 
  the 
  water 
  is 
  cold 
  enough, 
  we 
  meet 
  arctic 
  

   species, 
  and 
  wherever 
  it 
  is 
  warm 
  enough 
  we 
  have 
  Long 
  Island 
  

   species, 
  regardless 
  of 
  the 
  remoteness 
  of 
  localities 
  where 
  the 
  spe- 
  

   cies 
  naturally 
  abound, 
  and, 
  as 
  far 
  as 
  we 
  know, 
  of 
  the 
  absence 
  of 
  

   currents 
  to 
  transport 
  the 
  spores. 
  ' 
  ' 
  

  

  The 
  isolated 
  colonies 
  of 
  southern 
  shells, 
  ranging 
  from 
  

   north 
  of 
  Cape 
  Cod 
  to 
  the 
  Provinces 
  and 
  even 
  to 
  the 
  St. 
  

   Lawrence, 
  must 
  not 
  be 
  regarded 
  as 
  survivals 
  from 
  pre- 
  

   glacial 
  times 
  but 
  rather 
  as 
  introductions 
  in 
  later 
  days. 
  

   The 
  plankton 
  of 
  the 
  coast 
  is 
  charged 
  with 
  the 
  swimming 
  

   and 
  larval 
  stages 
  of 
  invertebrates, 
  and 
  spores 
  of 
  algae, 
  

   and 
  when 
  by 
  currents, 
  or 
  other 
  agencies, 
  these 
  objects 
  

   find 
  lodgment 
  in 
  favorable 
  regions 
  as 
  to 
  temperature 
  they 
  

   take 
  root 
  and 
  become 
  established. 
  The 
  spores 
  of 
  algae 
  

   could 
  unquestionably 
  be 
  transported 
  on 
  the 
  feet 
  of 
  aqua- 
  

   tic 
  birds. 
  

  

  The 
  most 
  common 
  species 
  of 
  mollusks 
  in 
  the 
  bowlder 
  

   clay 
  deposits 
  has 
  been 
  recognized 
  as 
  Venus 
  mercenaries. 
  

   Warren 
  Upham 
  says, 
  in 
  his 
  paper 
  on 
  Marine 
  Shells 
  and 
  

   Fragments 
  of 
  Shells 
  in 
  the 
  Till 
  near 
  Boston, 
  1 
  "In 
  all 
  the 
  

   localities 
  a 
  single 
  species, 
  the 
  round 
  clam, 
  or 
  quohaug, 
  

   Venus 
  mercenaria, 
  makes 
  up 
  probably 
  ninety-nine 
  per 
  

   cent 
  of 
  the 
  specimens 
  found, 
  but 
  no 
  entire 
  valve 
  of 
  the 
  

   shell 
  was 
  obtained 
  among 
  the 
  thousands 
  of 
  fragments.' 
  ' 
  

  

  In 
  nearly 
  every 
  reference 
  to 
  the 
  fragments 
  of 
  Venus 
  

   mercenaria 
  allusion 
  is 
  made 
  to 
  their 
  thick 
  and 
  massive 
  

   character. 
  Sanderson 
  Smith, 
  in 
  describing 
  the 
  post-plio- 
  

   cene 
  deposits 
  on 
  Gardiner's 
  Island, 
  Long 
  Island 
  Sound, 
  

   says, 
  2 
  ' 
  i 
  The 
  fragments 
  of 
  Venus 
  mercenaria 
  are 
  of 
  very 
  

   large 
  size 
  and 
  excessively 
  thick 
  and 
  heavy." 
  Prof. 
  A. 
  E. 
  

   Verrill, 
  in 
  a 
  paper 
  entitled 
  3 
  "On 
  the 
  Post-Pliocene 
  Fos- 
  

   sils 
  of 
  Sankaty 
  Head, 
  Nantucket 
  Island, 
  " 
  regards 
  the 
  

   Venus 
  mercenaria 
  as 
  a 
  distinct 
  variety 
  on 
  account 
  of 
  its 
  

  

  1 
  Proc. 
  B. 
  S. 
  N. 
  H., 
  vol. 
  24, 
  p. 
  127. 
  

  

  2 
  Annals 
  of 
  the 
  New 
  York 
  Lyceum 
  of 
  Natural 
  History, 
  vol. 
  8. 
  

  

  3 
  This 
  Journal, 
  vol. 
  10, 
  p. 
  364, 
  1875. 
  

  

  