﻿MOLLUSCA. 
  Ill 
  

  

  particularly 
  conspicuous 
  at 
  the 
  pallial 
  line, 
  where 
  they 
  terminate. 
  

   The 
  muscular 
  scars 
  are 
  large, 
  well 
  defiued 
  by 
  a 
  line 
  radiating 
  from 
  the 
  

   umbones. 
  Hinge-teeth 
  rather 
  numerous, 
  minute 
  in 
  the 
  centre, 
  

   considerably 
  larger 
  at 
  both 
  ends. 
  In 
  the 
  type 
  there 
  are 
  forty, 
  and 
  

   a 
  specimen 
  about 
  half-grown 
  has 
  thirty-five. 
  The 
  ligament 
  is 
  

   narrow, 
  but 
  very 
  coarsely 
  striated 
  transversely. 
  The 
  epidermis 
  is 
  

   thinnish 
  and 
  somewhat 
  fibrous 
  near 
  the 
  margins, 
  especially 
  pos- 
  

   teriorly. 
  

  

  59. 
  Area 
  (Barlbatia) 
  symmetrica. 
  

  

  Area 
  symmetrica, 
  Reeve, 
  Conch. 
  Icon, 
  sp, 
  117, 
  and 
  fig. 
  120. 
  

   ? 
  Var. 
  = 
  Area 
  zebuensis, 
  Reeve, 
  I. 
  c. 
  fig. 
  117, 
  sp. 
  120. 
  

  

  Hah. 
  Port 
  Molle, 
  Queensland, 
  12-20 
  fms. 
  (Copjpinger) 
  ; 
  Bay 
  of 
  

   Manila 
  {Cuminy). 
  

  

  In 
  the 
  ' 
  Conchologia 
  Iconica 
  ' 
  the 
  numbers 
  of 
  the 
  figures 
  120 
  

   and 
  117 
  should 
  be 
  reversed. 
  The 
  specimens 
  of 
  A. 
  symmetrica 
  

   which 
  were 
  described 
  by 
  Reeve 
  are 
  of 
  a 
  greenish 
  tint, 
  and 
  not 
  so 
  

   oblique 
  as' 
  A. 
  zebuensis. 
  The 
  sculpture 
  in 
  both 
  consists 
  of 
  fine 
  

   radiating 
  lirse, 
  rendered 
  minutely 
  granular 
  by 
  the 
  concentric 
  lines 
  

   of 
  growth. 
  The 
  liras 
  vary 
  but 
  little 
  in 
  thickness, 
  with 
  the 
  excep- 
  

   tion 
  of 
  a 
  few 
  finer 
  intermediate 
  ones 
  here 
  and 
  there 
  and 
  those 
  on 
  

   the 
  posterior 
  extremity, 
  which 
  are 
  a 
  trifle 
  stouter. 
  A. 
  zebuensis 
  

   differs, 
  in 
  addition 
  to 
  its 
  extra 
  obliquity 
  before 
  referred 
  to, 
  resulting 
  

   from 
  the 
  less 
  central 
  position 
  of 
  the 
  umbones, 
  in 
  being 
  a 
  trifle 
  more 
  

   finely 
  lirate. 
  One 
  of 
  the 
  specimens 
  from 
  Port 
  Molle 
  is 
  somewhat 
  

   intermediate 
  in 
  form, 
  being 
  more 
  oblique 
  than 
  A. 
  symmetrica 
  and 
  

   less 
  so 
  than 
  A. 
  zebuensis. 
  The 
  measurements 
  of 
  two 
  specimens 
  will 
  

   indicate 
  to 
  what 
  extent 
  the 
  form 
  and 
  proportions 
  may 
  vai'y 
  : 
  — 
  

  

  No. 
  1. 
  Height 
  7^ 
  millim., 
  length 
  11, 
  diameter 
  8, 
  

  

  No, 
  2, 
  „ 
  6i 
  „ 
  „ 
  11, 
  „ 
  6|. 
  

  

  60, 
  Area 
  (Trisis) 
  tortuosa. 
  

   Area 
  tortuosa, 
  Linn. 
  

  

  Hah. 
  Singapore 
  and 
  Malacca 
  {^Cuming'); 
  North-west 
  Australia 
  

   {Du 
  Boiday) 
  and 
  China 
  {Beeves), 
  in 
  Brit, 
  Mus, 
  ; 
  Port 
  Curtis 
  in 
  

   11 
  fms., 
  sand 
  and 
  shell 
  bottom 
  (Cojjjnnyer). 
  

  

  The 
  right 
  valve 
  of 
  this 
  well-known 
  and 
  remarkable 
  shell 
  always 
  

   appears 
  to 
  retain 
  more 
  of 
  the 
  epidermis 
  than 
  the 
  left. 
  The 
  foot 
  and 
  

   mouth 
  of 
  the 
  animal, 
  as 
  might 
  be 
  expected, 
  are 
  at 
  the 
  narrow 
  end 
  

   of 
  the 
  shell. 
  The 
  foot 
  (in 
  spirit) 
  is 
  small, 
  narrow, 
  and 
  grooved 
  

   beneath, 
  retaining 
  a 
  small 
  byssus. 
  

  

  61. 
  Leda 
  darwini. 
  (Plate 
  VII. 
  figs. 
  L-L2.) 
  

  

  Shell 
  a 
  little 
  inequilateral, 
  rather 
  convex, 
  transversely 
  irregularly 
  

   ovate, 
  acuminate 
  posteriorly, 
  thinnish, 
  glossy, 
  moderately 
  coarsely 
  

   concentrically 
  ridged 
  and 
  sulcate 
  throughout, 
  except 
  upon 
  the 
  lunule 
  

   and 
  area, 
  the 
  ridges 
  being 
  finer 
  and 
  the 
  sulci 
  broader 
  on 
  a 
  slightly 
  

   depressed 
  portion 
  of 
  the 
  surface 
  down 
  the 
  posterior 
  side, 
  which 
  is 
  of 
  

  

  