﻿AND 
  OTHER 
  FAMILIES. 
  67 
  

  

  on 
  the 
  posterior 
  part 
  ; 
  cardinal 
  teeth 
  double 
  in 
  both 
  valves, 
  compressed 
  

   and 
  erect; 
  lateral 
  teeth 
  very 
  long, 
  thin 
  and 
  nearly 
  straight; 
  anterior 
  

   cicatrices 
  distinct 
  ; 
  posterior 
  cicatrices 
  confluent 
  ; 
  dorsal 
  cicatrices 
  situ- 
  

   ated 
  in 
  the 
  cavity 
  of 
  the 
  beaks 
  ; 
  cavity 
  of 
  the 
  beaks 
  very 
  small 
  ; 
  nacre 
  

   beautifully 
  pearly 
  and 
  iridescent. 
  

  

  Remarks. 
  — 
  This 
  is 
  perhaps 
  the 
  most 
  extraordinary 
  Unio 
  that 
  has 
  

   yet 
  fallen 
  to 
  the 
  lot 
  of 
  a 
  naturalist 
  to 
  describe. 
  When 
  we 
  cast 
  our 
  

   eyes 
  over 
  all 
  the 
  species, 
  and 
  then 
  rest 
  them 
  on 
  this, 
  we 
  shall 
  be 
  ready 
  

   to 
  exclaim, 
  that 
  nothing 
  hereafter 
  belonging 
  to 
  this 
  genus 
  can 
  astonish 
  

   us. 
  Its 
  latitude 
  is 
  so 
  great, 
  that 
  one 
  at 
  first 
  sight 
  can 
  scarcely 
  believe 
  

   it 
  to 
  belong 
  to 
  the 
  family 
  Naiades. 
  Its 
  great 
  transverseness 
  causes 
  the 
  

   lateral 
  teeth 
  to 
  be 
  exceedingly 
  long, 
  and 
  that 
  character, 
  together 
  with 
  

   the 
  acutely 
  angular 
  posterior 
  margin, 
  gives 
  the 
  shell 
  the 
  form 
  of 
  a 
  

   crane's 
  beak. 
  In 
  outline 
  it 
  does 
  not 
  approach 
  any 
  species 
  I 
  know, 
  and 
  

   therefore 
  there 
  can 
  be 
  no 
  comparison 
  made. 
  I 
  procured 
  it 
  of 
  a 
  dealer 
  

   in 
  London, 
  and 
  dedicate 
  it 
  to 
  my 
  friend, 
  John 
  Edward 
  Gray, 
  Esq. 
  of 
  

   the 
  British 
  Museum, 
  one 
  of 
  the 
  most 
  distinguished 
  naturalists 
  in 
  Great 
  

   Britain, 
  and 
  to 
  whose 
  great 
  kindness 
  and 
  attention 
  while 
  in 
  London 
  I 
  

   am 
  much 
  indebted. 
  I 
  know 
  of 
  no 
  zoologist 
  who 
  has, 
  in 
  that 
  country, 
  

   pursued 
  our 
  favourite 
  science 
  with 
  more 
  ardour 
  or 
  more 
  success, 
  and 
  

   it 
  is 
  only 
  due 
  to 
  him, 
  while 
  it 
  gives 
  me 
  great 
  pleasure 
  to 
  render 
  him 
  

   this 
  tribute 
  of 
  respect 
  in 
  placing 
  his 
  name 
  to 
  one 
  of 
  the 
  most 
  inte- 
  

   resting 
  species 
  of 
  the 
  whole 
  family. 
  

  

  Unio 
  Burroughianus. 
  Plate 
  X. 
  fig. 
  27. 
  

  

  Testa 
  subrotunda, 
  insequilaterali, 
  compressd, 
  poslice 
  subangulata 
  j 
  nulibus 
  obli- 
  

   que 
  plicatis 
  , 
  prominulis 
  ; 
  valvulis 
  subcrassis 
  ; 
  epidermide 
  tenebroso-fuscd 
  ; 
  dentibus 
  

   cardinalibus 
  magnis, 
  elevatis 
  et 
  laminatis, 
  lateralibus 
  subrecfis 
  ; 
  margariid 
  alba 
  

   et 
  iridescente. 
  

  

  Shell 
  subrotund, 
  inequilateral, 
  compressed, 
  subangular 
  behind, 
  with 
  oblique 
  folds 
  on 
  

   the 
  beaks 
  ; 
  valves 
  rather 
  thick 
  ; 
  beaks 
  somewhat 
  elevated 
  and 
  much 
  plicate 
  ; 
  epidermis 
  

   dark 
  brown 
  ; 
  cardinal 
  teeth 
  large, 
  elevated 
  and 
  lamelliform 
  ; 
  lateral 
  teeth 
  nearly 
  straight; 
  

   nacre 
  pearly 
  white 
  and 
  iridescent. 
  

  

  