﻿AND 
  OTHER 
  FAMILIES. 
  69 
  

  

  Shell 
  subtriangular, 
  inflated, 
  singularly 
  compressed 
  on 
  the 
  posterior 
  part, 
  which 
  is 
  

   striate 
  ; 
  valves 
  remarkably 
  thick 
  ; 
  beaks 
  very 
  prominent 
  ; 
  cardinal 
  teeth 
  large 
  ; 
  late- 
  

   ral 
  teeth 
  thick 
  and 
  nearly 
  straight 
  ; 
  nacre 
  in 
  the 
  cavity 
  very 
  light 
  purple. 
  

  

  Hab. 
  Tennessee. 
  G. 
  B. 
  Sowerby. 
  

  

  My 
  Cabinet. 
  

  

  Cabinet 
  of 
  Mr 
  Sowerby. 
  

  

  Diam. 
  1-5, 
  Length 
  1-7, 
  Breadth 
  1-8 
  inches. 
  

  

  Shell 
  subtriangular, 
  inflated, 
  singularly 
  compressed 
  on 
  the 
  posterior 
  

   part, 
  which 
  is 
  filled 
  with 
  striae 
  passing 
  from 
  the 
  beak 
  to 
  the 
  posterior 
  

   and 
  posterior-basal 
  margins, 
  the 
  anterior 
  part 
  being 
  inflated 
  and 
  smooth 
  ; 
  

   slightly 
  emarginate 
  at 
  posterior 
  basal 
  margin 
  ; 
  substance 
  of 
  the 
  shell 
  

   very 
  remarkably 
  thick, 
  less 
  so 
  on 
  the 
  posterior 
  part 
  ; 
  beaks 
  large 
  and 
  

   very 
  prominent 
  ; 
  ligament 
  short 
  and 
  thick 
  ; 
  epidermis 
  bright 
  brown, 
  

   smooth 
  and 
  shining 
  before, 
  striate 
  behind; 
  cardinal 
  teeth 
  large, 
  sulcate, 
  

   elevated 
  and 
  cleft 
  in 
  the 
  left 
  valve, 
  and 
  emerging 
  from 
  a 
  pit 
  in 
  the 
  

   right 
  valve 
  ; 
  lateral 
  teeth 
  thick, 
  short 
  and 
  nearly 
  straight 
  ; 
  anterior 
  and 
  

   posterior 
  cicatrices 
  both 
  distinct 
  ; 
  dorsal 
  cicatrices 
  situated 
  on 
  the 
  under 
  

   part 
  of 
  the 
  cardinal 
  teeth 
  ; 
  cavity 
  of 
  the 
  beaks 
  shallow 
  and 
  subangular 
  ; 
  

   nacre 
  very 
  light 
  purple 
  in 
  the 
  cavity, 
  and 
  white 
  on 
  the 
  anterior 
  margin. 
  

  

  Remarks. 
  — 
  To 
  the 
  kindness 
  of 
  G. 
  B. 
  Sowerby, 
  Esq., 
  one 
  of 
  the 
  

   most 
  distinguished 
  writers 
  on 
  conchology 
  in 
  England, 
  I 
  owe 
  the 
  pos- 
  

   session 
  of 
  this 
  truly 
  interesting 
  shell, 
  and 
  to 
  him 
  I 
  with 
  great 
  pleasure 
  

   dedicate 
  it. 
  He 
  received 
  it 
  from 
  the 
  state 
  of 
  Tennessee, 
  but 
  from 
  

   what 
  river 
  I 
  do 
  not 
  know. 
  In 
  general 
  outline 
  it 
  resembles 
  somewhat 
  

   the 
  trigonus 
  (nobis), 
  but 
  differs 
  from 
  it 
  in 
  being 
  more 
  rotund, 
  in 
  hav- 
  

   ing 
  the 
  posterior 
  part 
  compressed 
  and 
  striate, 
  and 
  in 
  being 
  coloured 
  

   inside. 
  It 
  has 
  a 
  stronger 
  resemblance 
  to 
  the 
  Haysianus 
  (nobis) 
  than 
  to 
  

   any 
  other 
  species 
  known 
  to 
  me, 
  but 
  diners 
  from 
  it 
  in 
  being 
  more 
  com- 
  

   pressed 
  behind, 
  in 
  being 
  more 
  striate, 
  in 
  being 
  much 
  larger 
  (to 
  judge 
  

   from 
  the 
  few 
  specimens 
  I 
  have 
  seen 
  of 
  both), 
  and 
  in 
  the 
  difference 
  of 
  

   the 
  colour 
  of 
  the 
  nacre, 
  the 
  Haysianus 
  being 
  dark 
  chocolate, 
  while 
  the 
  

   Sowerbianus 
  is 
  of 
  a 
  very 
  light 
  purple, 
  approaching 
  to 
  flesh 
  colour. 
  

  

  vol. 
  v. 
  — 
  s 
  

  

  