﻿134 
  Mr. 
  A. 
  J. 
  Jukes-Browne 
  on 
  

  

  few 
  specimens 
  have 
  come 
  into 
  the 
  possession 
  of 
  concho- 
  

   logists. 
  

  

  Having 
  recently 
  received 
  a 
  shell 
  from 
  Mr. 
  Y. 
  Hirase, 
  of 
  

   Kyoto 
  (Japan), 
  which 
  I 
  felt 
  sure 
  must 
  be 
  V. 
  stimpsoni, 
  as 
  it 
  

   was 
  clearly 
  a 
  Mercenaria, 
  and 
  that 
  is 
  the 
  only 
  Japanese 
  

   species 
  of 
  the 
  group, 
  I 
  wrote 
  to 
  Mr. 
  E. 
  A. 
  Smith 
  about 
  it. 
  

   He 
  sent 
  me 
  a 
  copy 
  of 
  Gould's 
  description, 
  but 
  informed 
  me 
  

   that 
  the 
  Museum 
  did 
  not 
  possess 
  a 
  specimen, 
  and 
  advised 
  

   me 
  to 
  have 
  the 
  shell 
  compared 
  with 
  the 
  type 
  in 
  the 
  United 
  

   States 
  Museum. 
  Accordingly 
  I 
  sent 
  it 
  to 
  Dr. 
  P. 
  Bartsch, 
  

   who 
  has 
  kindly 
  compared 
  it 
  with 
  the 
  type 
  and 
  informs 
  me 
  

   that 
  it 
  is 
  undoubtedly 
  the 
  V. 
  stimpsoni 
  of 
  Gould. 
  

  

  Under 
  these 
  circumstances 
  it 
  seems 
  desirable 
  that 
  the 
  shell 
  

   should 
  be 
  figured 
  and 
  more 
  fully 
  described 
  in 
  English, 
  for 
  

   Gould's 
  description 
  was 
  in 
  Latin 
  only, 
  and 
  ran 
  as 
  follows 
  : 
  — 
  

  

  a 
  Venus 
  (Mercenaria) 
  stimpsoni. 
  T. 
  [/. 
  e. 
  Testa] 
  solida, 
  

   cinerea, 
  ovato-cordata, 
  satis 
  convexa, 
  laminis 
  erectis 
  con- 
  

   centricis 
  confertrs 
  disposite 
  ornata 
  ; 
  umbonibus 
  antemedianis 
  

   eminentibus, 
  acutis, 
  approximatis; 
  facie 
  d.orsali 
  antica 
  con- 
  

   cava 
  ; 
  lunula 
  profunda; 
  extremitate 
  antica 
  compressa, 
  

   rotundata 
  ; 
  facie 
  dorsali 
  postica 
  arcuata, 
  declivi, 
  impressa, 
  

   nihil 
  nisi 
  striata; 
  extremitate 
  posticd 
  satis 
  acuta: 
  cardo 
  

   validus; 
  cavositas 
  et 
  apophysis 
  ligamentalis 
  aurantiaci 
  ; 
  

   sinu 
  siphonali 
  minime 
  profundo 
  ; 
  margine 
  interna 
  simplici. 
  

   Long. 
  3'7 
  ; 
  alt. 
  3'3 
  ; 
  lat. 
  1*7 
  poll. 
  Inhabits 
  Hakodadi, 
  

   6 
  fathoms." 
  

  

  The 
  Mercenaria 
  group 
  belongs 
  to 
  what 
  should 
  be 
  regarded 
  

   as 
  the 
  restricted 
  genus 
  Venus, 
  though 
  I 
  have 
  come 
  to 
  that 
  

   conclusion 
  on 
  different 
  grounds 
  from 
  Dr. 
  Dall, 
  and 
  differ 
  from 
  

   him 
  in 
  regarding 
  the 
  genus 
  as 
  a 
  much 
  more 
  comprehensive 
  

   group, 
  for 
  I 
  can 
  see 
  no 
  geneiic 
  distinction 
  between 
  it 
  and 
  

   Chione. 
  

  

  The 
  characters 
  possessed 
  in 
  common 
  by 
  Mercenaria 
  and 
  

   Chione 
  are 
  : 
  that 
  the 
  external 
  sculpture 
  of 
  the 
  shell 
  is 
  more 
  

   or 
  ltss 
  cancellate, 
  the 
  concentric 
  lamellae 
  predominating, 
  but 
  

   the 
  radiate 
  riblets 
  show 
  themselves 
  in 
  the 
  crenulated 
  inner 
  

   margins 
  of 
  the 
  valves 
  ; 
  that 
  the 
  lunule 
  is 
  impressed 
  and 
  the 
  

   escutcheon 
  is 
  well 
  defined 
  ; 
  that 
  all 
  have 
  a 
  thick 
  hinge-plate, 
  

   bearing 
  three 
  cardinal 
  teeth, 
  but 
  no 
  laterals 
  ; 
  and, 
  finally, 
  that 
  

   the 
  pallial 
  sinus 
  is 
  small, 
  triangular, 
  and 
  pointed. 
  

  

  Mercenaria 
  differs 
  from 
  the 
  typical 
  Chione 
  in 
  always 
  

   having 
  a 
  rugose 
  area 
  on 
  the 
  nymphal 
  plate 
  of 
  the 
  right 
  valve 
  

   and 
  on 
  the 
  back 
  of 
  the 
  posterior 
  tooth 
  of 
  the 
  left 
  ; 
  such 
  areas 
  

   being 
  only 
  present 
  in 
  a 
  few 
  species 
  of 
  Chione. 
  The 
  posterior 
  

   and 
  middle 
  teeth 
  of 
  the 
  right 
  valve 
  are 
  deeply 
  grooved 
  or 
  

  

  