﻿IDENTIFICATION 
  OF 
  THE 
  GLOCHIDIA 
  OF 
  FRESH- 
  WATER 
  MUSSELS, 
  

  

  By 
  Thaddeus 
  Surber, 
  

   Assistant, 
  United 
  States 
  Biological 
  Laboratory, 
  Fairport, 
  Iowa. 
  

  

  In 
  investigations 
  with 
  reference 
  to 
  the 
  natural 
  hosts 
  of 
  our 
  fresh- 
  

   water 
  mussels, 
  the 
  identification 
  of 
  certain 
  larval 
  forms 
  at 
  times 
  

   becomes 
  one 
  of 
  extreme 
  difficulty, 
  owing 
  to 
  the 
  close 
  resemblance 
  of 
  

   certain 
  species 
  one 
  to 
  another. 
  Fortunately, 
  so 
  far 
  as 
  known, 
  the 
  

   glochidial 
  shell 
  is 
  retained 
  intact, 
  even 
  after 
  metamorphosis 
  in 
  many 
  

   instances, 
  so 
  that 
  if 
  the 
  observer 
  Imows 
  the 
  glochidium, 
  its 
  form, 
  size, 
  

   and 
  peculiarities, 
  the 
  identification 
  is 
  somewhat 
  simplified, 
  even 
  

   though 
  the 
  marginal 
  growth 
  of 
  the 
  infant 
  mussel 
  shell 
  is 
  greatly 
  

   mcreased 
  m 
  size 
  and 
  the 
  shape 
  modified. 
  Believing 
  that 
  much 
  use- 
  

   less 
  experimentation 
  could 
  be 
  avoided 
  by 
  the 
  discovery 
  of 
  the 
  natural 
  

   hosts 
  of 
  the 
  various 
  species, 
  much 
  time 
  has 
  been 
  devoted 
  to 
  this 
  end, 
  

   but 
  at 
  the 
  same 
  time 
  it 
  has 
  not 
  been 
  forgotten 
  that 
  the 
  first 
  requisite 
  

   is 
  a 
  collection 
  of 
  the 
  glochidia 
  of 
  the 
  various 
  species 
  found 
  in 
  the 
  

   region 
  worked 
  over. 
  The 
  accumulation 
  of 
  such 
  a 
  collection 
  presents 
  

   difficulties, 
  as 
  the 
  breeding 
  seasons 
  of 
  certam 
  forms 
  have 
  long 
  been 
  

   unknown, 
  particularly 
  of 
  the 
  rarer 
  forms. 
  The 
  staff 
  of 
  the 
  Fairport 
  

   Biological 
  Laboratory 
  have 
  kept 
  this 
  important 
  object 
  in 
  mind, 
  and, 
  

   wliile 
  conducting 
  field 
  work 
  in 
  various 
  parts 
  of 
  the 
  Mississippi 
  Valley, 
  

   have 
  from 
  time 
  to 
  time 
  sent 
  m 
  glochidia 
  of 
  those 
  species 
  found 
  in 
  the 
  

   vicinity 
  of 
  Fairport 
  so 
  rarely 
  as 
  to 
  elude 
  us 
  at 
  the 
  proper 
  season, 
  and 
  

   in 
  addition 
  an 
  occasional 
  species 
  not 
  native 
  to 
  our 
  local 
  waters. 
  It 
  

   has 
  therefore 
  been 
  possible, 
  since 
  the 
  pubUcation 
  of 
  my 
  former 
  paper 
  

   on 
  the 
  glochidia," 
  practically 
  to 
  complete 
  the 
  collection 
  of 
  local 
  forms, 
  

   the 
  only 
  desiderata 
  now 
  being 
  Lampsilis 
  leptodon 
  and 
  Truncilla 
  tri- 
  

   quetra, 
  both 
  of 
  which 
  are 
  extremely 
  rare 
  in 
  the 
  Mississippi 
  in 
  this 
  

   vicinity. 
  The 
  former, 
  in 
  fact, 
  is 
  a 
  rather 
  rare 
  shell 
  wherever 
  found. 
  

  

  In 
  the 
  paper 
  before 
  referred 
  to 
  I 
  gave 
  an 
  analytical 
  key 
  for 
  identi- 
  

   fication 
  of 
  the 
  glochidia 
  figured. 
  This 
  is 
  not 
  attempted 
  in 
  the 
  present 
  

   instance, 
  as 
  the 
  species 
  are 
  so 
  few 
  it 
  is 
  thought 
  that 
  descriptions 
  and 
  

   figures 
  wiU 
  suffice. 
  These 
  descriptions 
  show, 
  by 
  comparison, 
  the 
  

   relationship 
  with 
  other 
  forms 
  so 
  far 
  as 
  size 
  and 
  general 
  characters 
  are 
  

   concerned. 
  If 
  the 
  reader 
  so 
  desires, 
  however, 
  the 
  position 
  of 
  the 
  

   forms 
  here 
  described 
  can 
  easily 
  be 
  determined 
  and 
  placed 
  in 
  proper 
  

  

  a 
  Surber, 
  Thaddeus: 
  Identification 
  of 
  the 
  glochidia 
  of 
  fresh-water 
  mussels. 
  Bureau 
  of 
  Fisheries 
  Docu- 
  

   ment 
  no. 
  771, 
  10 
  p., 
  3 
  pi. 
  (47 
  fig.), 
  1912. 
  

  

  