﻿MUSSEL 
  KESOUKCES 
  OF 
  THE 
  ILLINOIS 
  RIVER, 
  43 
  

  

  are 
  seen 
  floating 
  along 
  with 
  the 
  current; 
  hence 
  the 
  common 
  name 
  of 
  

   ''floater." 
  Grandis 
  and 
  corpulenta 
  are 
  often 
  affected 
  with 
  parasites, 
  

   particularly 
  at 
  the 
  posterior 
  end. 
  Our 
  examples 
  were 
  all 
  of 
  only 
  

   moderate 
  size 
  as 
  compared 
  with 
  shells 
  seen 
  in 
  retired 
  places 
  along 
  the 
  

   Cumberland. 
  

  

  28. 
  Anodonta 
  suhorbiculata 
  (Say). 
  — 
  Suborbiculata 
  is 
  widely 
  dis- 
  

   tributed 
  and 
  is 
  generally 
  found 
  on 
  mud 
  bottoms 
  and 
  in 
  slack 
  water. 
  

  

  29. 
  Anodonta 
  imhecillis 
  (Say). 
  — 
  This 
  small, 
  delicate 
  shell 
  is 
  very 
  

   abundantly 
  distributed, 
  especially 
  in 
  the 
  more 
  retired 
  places 
  of 
  quiet 
  

   waters. 
  Found 
  gravid 
  Jmie 
  27 
  and 
  July 
  2, 
  

  

  30. 
  Sqv 
  AW-FOOT, 
  Stropliitus 
  edentulus 
  (SsLj). 
  — 
  Found 
  rather 
  scat- 
  

   tering 
  throughout 
  the 
  various 
  stretches 
  and 
  mussel 
  beds 
  of 
  the 
  river. 
  

   The 
  nacre 
  is 
  usually 
  of 
  a 
  yellowish 
  color. 
  This 
  shell 
  has 
  no 
  particular 
  

   commercial 
  value, 
  although 
  some 
  examples 
  are 
  found 
  which 
  are 
  of 
  

   sufficient 
  thickness 
  and 
  size 
  for 
  manufacturing 
  purposes. 
  

  

  31. 
  Three-horned 
  Shell, 
  OUiquaria 
  rejlexa 
  (Rafinesque). 
  — 
  This 
  

   mussel 
  is 
  widely 
  distributed 
  and 
  is 
  usually 
  of 
  small 
  size. 
  There 
  are 
  

   two 
  or 
  three 
  forms 
  of 
  rejlexa 
  found 
  in 
  the 
  IlUnois. 
  In 
  the 
  upper 
  

   stretches 
  of 
  the 
  river 
  it 
  is 
  of 
  the 
  ordinary 
  shape 
  and 
  size 
  found 
  in 
  

   other 
  streams, 
  and 
  although 
  it 
  can 
  be 
  used 
  for 
  manufacturing 
  pur- 
  

   poses 
  it 
  is 
  not 
  a 
  particularly 
  valuable 
  shell 
  to 
  propagate. 
  In 
  the 
  

   Peoria 
  Lake 
  region, 
  however, 
  where 
  the 
  current 
  is 
  slow 
  and 
  the 
  bot- 
  

   tom 
  is 
  composed 
  of 
  soft 
  mud, 
  the 
  shell 
  is 
  often 
  very 
  heavy 
  and 
  rounded 
  

   anteriorly, 
  while 
  posteriorly 
  it 
  is 
  tliin 
  and 
  much 
  elongated, 
  which 
  no 
  

   doubt 
  is 
  the 
  result 
  of 
  accommodation 
  to 
  natural 
  conditions. 
  In 
  the 
  

   lower 
  stretches 
  the 
  shell, 
  though 
  heavy 
  and 
  inflated, 
  is 
  considerably 
  

   smaUer 
  than 
  those 
  in 
  the 
  upper 
  portions 
  of 
  the 
  river. 
  A 
  number 
  of 
  

   our 
  examples 
  have 
  five 
  tubercules 
  on 
  each 
  valve. 
  Found 
  gravid 
  

   June 
  27 
  and 
  July 
  3. 
  

  

  32. 
  BucKHORN, 
  Pistol-grip, 
  Tritogonia 
  tuherculata 
  (Barnes). 
  — 
  

   Although 
  this 
  interesting 
  species 
  is 
  comparatively 
  rare 
  in 
  the 
  IlUnois, 
  it 
  

   is 
  widely 
  distributed. 
  The 
  name 
  of 
  pistol-grip 
  is 
  applied 
  to 
  it 
  in 
  some 
  

   locahties, 
  owing 
  to 
  the 
  fact 
  that 
  it 
  fits 
  the 
  haaid 
  like 
  a 
  pistol. 
  The 
  

   characteristic 
  ridge 
  of 
  this 
  shell 
  gives 
  it 
  somewhat 
  the 
  appearance 
  of 
  

   the 
  abnormal 
  ridge 
  found 
  occasionally 
  on 
  the 
  heros 
  or 
  washboard 
  as 
  

   the 
  result 
  of 
  pearl 
  growth. 
  Wliile 
  tliis 
  shell 
  has 
  a 
  ridge 
  on 
  each 
  valve, 
  

   the 
  abnormal 
  washboard 
  has 
  but 
  one 
  valve 
  ridged, 
  the 
  other 
  having 
  

   a 
  corresponding 
  valley. 
  

  

  The 
  buckhorn 
  furnishes 
  good 
  material 
  for 
  the 
  manufacture 
  of 
  

   buttons 
  and 
  novelties. 
  

  

  33. 
  Little 
  Pocketbook, 
  PZa^ioZa 
  (ionaci/ormis 
  (Lea). 
  — 
  This 
  small 
  

   mussel, 
  although 
  of 
  no 
  commercial 
  value, 
  is 
  very 
  common 
  in 
  the 
  

   Illinois. 
  Tliere 
  are 
  two 
  types 
  of 
  this 
  species 
  found 
  in 
  many 
  beds, 
  

   differing 
  in 
  shape 
  to 
  a 
  certain 
  extent 
  and 
  particularly 
  in 
  color. 
  On 
  

  

  