﻿516 
  Panama 
  Shells. 
  mactrid^. 
  

  

  491. 
  Amphidesma 
  Tentricosiini. 
  Nov. 
  sp. 
  

  

  Shell 
  suborbicular, 
  subequilateral, 
  ventricose, 
  flexuous 
  ; 
  with 
  

   the 
  anterior 
  and 
  posterior 
  dorsal 
  margins 
  nearly 
  straight; 
  with 
  

   the 
  margins 
  otherwise 
  well 
  rounded 
  : 
  dingy 
  white, 
  brownish 
  in 
  

   ill-defined 
  zones 
  : 
  with 
  unequal 
  striae 
  of 
  growth 
  ; 
  densely 
  

   covered 
  with 
  radiating 
  microscopic 
  striae 
  : 
  beaks 
  small, 
  approxi- 
  

   mate 
  : 
  umbones 
  very 
  convex 
  : 
  corselet 
  and 
  lunule 
  not 
  very 
  well 
  

   defined. 
  

  

  Length 
  .7 
  inch 
  ; 
  height 
  .62 
  inch 
  ; 
  breadth 
  .86 
  inch. 
  

  

  Station. 
  — 
  Unknown. 
  

  

  Habitat. 
  — 
  Panama 
  ; 
  C. 
  B. 
  A. 
  ! 
  

   A 
  single 
  valve 
  only 
  was 
  found. 
  

  

  492. 
  Crassatella 
  gribbosa. 
  

  

  Synonymy. 
  

  

  Crassatella 
  gibbosa 
  Sowb. 
  in 
  Proc. 
  Zool. 
  Soc. 
  Lond. 
  p. 
  56. 
  Mar. 
  1832. 
  

  

  Mull. 
  Syn. 
  Test. 
  Viv. 
  p. 
  212. 
  May 
  1836. 
  

  

  Reeve 
  Conch. 
  Syst. 
  I. 
  pi. 
  44. 
  f. 
  2. 
  Sept. 
  1841. 
  

  

  Reeve 
  Conch. 
  Icon. 
  pi. 
  1. 
  f. 
  1. 
  Jan. 
  1843, 
  

  

  Hanley 
  Supp. 
  Wood 
  Ind. 
  Test. 
  pi. 
  12. 
  f. 
  16. 
  1845 
  ? 
  

  

  Hanley 
  Descr. 
  Catal. 
  p. 
  37. 
  1845 
  ? 
  

  

  Chenu 
  111. 
  Conch, 
  pi. 
  2. 
  f. 
  6, 
  12. 
  

  

  Orb. 
  Voy. 
  Amer. 
  Merid. 
  Moll. 
  p. 
  578. 
  1846. 
  

  

  Station. 
  — 
  Sandy 
  mud, 
  11 
  fathoms 
  ; 
  Cuming 
  ! 
  Sowerby 
  : 
  also 
  

   Eeeve. 
  

  

  Habitat. 
  — 
  St. 
  Elena 
  and 
  Xipixapi 
  ; 
  Cuming 
  ! 
  Sowerby 
  : 
  also 
  

   Miiller 
  : 
  also 
  Orbigny 
  : 
  also 
  Eeeve. 
  

  

  Payta; 
  Fontaine! 
  Orbigny. 
  

  

  S. 
  America 
  ; 
  Hanley. 
  

  

  Punta 
  St. 
  Elena 
  ; 
  Jay. 
  

  

  Panama 
  ; 
  C. 
  B. 
  A 
  I 
  

   Only 
  1 
  valve 
  was 
  obtained. 
  

  

  