﻿Venus 
  stimpsoni, 
  Gould. 
  135 
  

  

  bifid, 
  as 
  also 
  is 
  the 
  median 
  of 
  the 
  left; 
  whereas 
  in 
  many 
  of 
  

   the 
  adult 
  Chi 
  one 
  the 
  teeth 
  are 
  entire 
  or 
  only 
  feebly 
  grooved. 
  

  

  Specifically 
  Venus 
  stint 
  psoni 
  may 
  be 
  described 
  as 
  follows 
  : 
  — 
  

   Shell 
  large, 
  solid, 
  triangularly-ovate, 
  more 
  attenuated 
  poste- 
  

   riorly 
  than 
  other 
  species, 
  the 
  postero-dorsal 
  slope 
  being 
  

   flattened 
  and 
  elongated 
  so 
  as 
  to 
  meet 
  the 
  postero-ventral 
  

   slope 
  in 
  an 
  angle 
  which 
  approximately 
  subtends 
  the 
  median 
  

   transverse 
  diameter 
  of 
  the 
  shell. 
  The 
  anterior 
  side 
  is 
  evenly 
  

   rounded 
  and 
  somewhat 
  compressed. 
  The, 
  specimen 
  measures 
  

   a 
  little 
  over 
  3h 
  inches 
  in 
  length 
  by 
  2f 
  in 
  height 
  ; 
  more 
  

   accurately 
  it 
  is 
  9 
  cent, 
  long 
  by 
  7'3 
  cent, 
  high 
  across 
  the 
  

   middle 
  of 
  the 
  shell. 
  

  

  The 
  sculpture 
  consists 
  of 
  numerous 
  low 
  concentric 
  lamellae 
  

   which 
  are 
  very 
  close-set 
  on 
  the 
  two 
  sides 
  and 
  near 
  the 
  ventral 
  

   border 
  of 
  the 
  valves. 
  On 
  the 
  central 
  part 
  of 
  each 
  valve 
  the 
  

   spaces 
  between 
  the 
  lamella} 
  are 
  striated 
  concentrically 
  but 
  

   irregularly, 
  and 
  are 
  also 
  crossed 
  by 
  faint 
  radiating 
  lines. 
  

   The 
  valves 
  are 
  somewhat 
  compressed, 
  so 
  that 
  the 
  width 
  from 
  

   centre 
  to 
  centre 
  is 
  loss 
  than 
  in 
  V. 
  mercenaria 
  and 
  the 
  shell 
  is 
  

   consequently 
  less 
  ventrieose. 
  

  

  The 
  internal 
  characters 
  are 
  like 
  those 
  of 
  V. 
  mercenaria, 
  

   but 
  the 
  rugose 
  areas 
  of 
  the 
  hinge 
  are 
  narrower 
  and 
  less 
  

   pronounced. 
  The 
  pallial 
  sinus 
  is 
  rather 
  smaller, 
  and 
  the 
  

   muscular 
  scars 
  rather 
  larger 
  than 
  in 
  the 
  type 
  species. 
  The 
  

   crenulated 
  inner 
  margin 
  of 
  ihe 
  valves 
  is 
  very 
  narrow 
  and 
  the 
  

   crcnulations 
  on 
  the 
  lunular 
  margin 
  are 
  faint. 
  Still 
  the 
  

   margins 
  are 
  not 
  " 
  simple'" 
  as 
  stated 
  by 
  Mr. 
  Gould 
  ; 
  possibly 
  

   his 
  specimen 
  was 
  somewhat 
  worn. 
  

  

  The 
  Mercenaria 
  section 
  of 
  Venus 
  is 
  almost 
  entirely 
  

   American, 
  V. 
  stimpsoni 
  being 
  the 
  only 
  species 
  yet 
  recognized 
  

   outside 
  American 
  waters, 
  though 
  some 
  Australasian 
  species, 
  

   such 
  as 
  V. 
  yatei. 
  Gray, 
  and 
  V. 
  alata, 
  Reeve, 
  come 
  very 
  near 
  

   to 
  it. 
  

  

  There 
  are 
  two 
  species 
  on 
  the 
  east 
  coast 
  of 
  America, 
  

   V. 
  mercenaria, 
  Linn., 
  and 
  V. 
  campechiensis, 
  Gmelin 
  ( 
  = 
  

   V. 
  mortoni, 
  Conrad). 
  Two 
  also 
  occur 
  on 
  the 
  west 
  coast, 
  

   viz., 
  V. 
  kennicotti, 
  Dall, 
  and 
  V. 
  apodema, 
  Dall, 
  but 
  both 
  are 
  

   very 
  rare. 
  V. 
  stimpsoni 
  is 
  probably 
  most 
  nearly 
  allied 
  to 
  

   V. 
  kennicotti, 
  for 
  Dr. 
  Dall 
  describes 
  this 
  latter 
  species 
  as 
  

   being 
  yellowish 
  white 
  in 
  colour 
  and 
  closely 
  lamellose 
  over 
  

   the 
  whole 
  surface 
  ; 
  he 
  also 
  says 
  fl 
  the 
  rugose 
  area 
  of 
  the 
  

   hinge 
  is 
  more 
  narrow 
  and 
  delicate 
  than 
  in 
  the 
  Atlantic 
  

   species, 
  but 
  this 
  area 
  is 
  still 
  further 
  diminished 
  in 
  the 
  

   Japanese 
  V. 
  stimpsoni 
  (Gould), 
  the 
  only 
  exotic 
  species 
  of 
  the 
  

   group." 
  

  

  