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  PHOCEEDIN"GS 
  OF 
  THE 
  3IAL1C0L0GICAL 
  SOCIETY. 
  

  

  supported 
  by 
  a 
  shelly 
  plate 
  behind 
  the 
  teeth. 
  The 
  hinge-plate 
  is 
  

   narrow, 
  delicate, 
  and 
  excavated, 
  bearing 
  three 
  teeth 
  in 
  the 
  left 
  valve 
  

   and 
  two 
  in 
  the 
  right. 
  The 
  teeth 
  are 
  all 
  narrow, 
  prominent, 
  and 
  near 
  

   together, 
  hardly 
  divergent 
  ; 
  the 
  left 
  central 
  and 
  posterior 
  being 
  

   grooved, 
  but 
  not 
  exactly 
  bifid 
  in 
  any 
  I 
  have 
  seen. 
  The 
  pallial 
  line 
  

   has 
  a 
  long 
  deep 
  sinus. 
  

  

  Dr. 
  Dall 
  created 
  a 
  separate 
  family 
  for 
  this 
  genus 
  in 
  the 
  memoir 
  

   above 
  cited, 
  but 
  gave 
  no 
  reason 
  for 
  so 
  doing, 
  leaving 
  us 
  to 
  suppose 
  

   that 
  he 
  regarded 
  the 
  presence 
  of 
  a 
  semi-internal 
  resilium 
  and 
  very 
  

   thin 
  shell 
  as 
  characters 
  of 
  family 
  importance. 
  For 
  such 
  separation 
  

   I 
  see 
  no 
  necessity, 
  though 
  I 
  agree 
  with 
  him 
  as 
  to 
  the 
  close 
  affinitj" 
  of 
  

   Cooper 
  ella 
  with 
  the 
  Petricolidse. 
  

  

  3. 
  Description 
  oe 
  Animals. 
  

  

  Petricola. 
  — 
  I 
  cannot 
  find 
  that 
  anyone 
  has 
  yet 
  described 
  the 
  animal 
  

   of 
  the 
  small 
  tj'pical 
  section 
  of 
  Petricola, 
  which 
  was 
  called 
  Naranio 
  by 
  

   Gray. 
  Writing 
  in 
  1853 
  he 
  says 
  of 
  it 
  " 
  animal 
  ignotum 
  " 
  ; 
  but 
  

   probably 
  it 
  resembles 
  that 
  of 
  the 
  Rupellaria 
  section. 
  

  

  Rnpellaria. 
  — 
  The 
  descriptions 
  of 
  the 
  animal 
  of 
  Petricola 
  given 
  by 
  

   S. 
  P. 
  Woodward 
  and 
  the 
  Messrs. 
  Adams 
  doubtless 
  refer 
  to 
  the 
  

   Mediterranean 
  species 
  P. 
  lithophaga. 
  They 
  say 
  the 
  mantle 
  is 
  closed 
  

   in 
  front, 
  thickened 
  and 
  recurved 
  over 
  the 
  edges 
  of 
  the 
  shell 
  ; 
  the 
  

   siphons 
  are 
  separate 
  for 
  the 
  greater 
  part 
  of 
  their 
  length 
  ; 
  the 
  foot 
  is 
  

   small, 
  compressed, 
  and 
  lanceolate, 
  with 
  a 
  byssal 
  groove 
  on 
  the 
  lower 
  

   margin. 
  

  

  These 
  characters 
  are 
  evidently 
  correlated 
  with 
  the 
  boring 
  habit 
  of 
  

   the 
  animal 
  ; 
  the 
  foot 
  being 
  small, 
  because 
  there 
  is 
  small 
  use 
  for 
  it 
  in 
  

   the 
  limited 
  space 
  within 
  which 
  the 
  animal 
  lives. 
  

  

  Petricolaria. 
  — 
  The 
  animal 
  of 
  this 
  group 
  is 
  similar 
  to 
  that 
  of 
  

   Rupellaria, 
  but 
  is, 
  of 
  course, 
  much 
  elongated 
  posteriorly. 
  The 
  foot, 
  

   however, 
  is 
  much 
  larger, 
  a 
  fact 
  which 
  seems 
  to 
  indicate 
  that 
  the 
  

   animal 
  has 
  freer 
  movement 
  within 
  its 
  soft-walled 
  burrow, 
  and 
  uses 
  

   its 
  foot 
  as 
  a 
  fulcrum. 
  The 
  siphons 
  are 
  separate, 
  divergent, 
  and 
  

   remarkably 
  long. 
  

  

  Lajonkairea. 
  — 
  The 
  only 
  description 
  which 
  I 
  have 
  been 
  able 
  to 
  find 
  

   of 
  this 
  animal 
  is 
  that 
  given 
  by 
  Deshayes 
  in 
  Latin, 
  ^ 
  of 
  which 
  the 
  

   following 
  is 
  a 
  translation 
  : 
  — 
  " 
  Mantle 
  entire, 
  open 
  in 
  front, 
  closed 
  

   below 
  and 
  behind 
  ; 
  siphons 
  two, 
  united 
  to 
  one 
  another, 
  somewhat 
  

   compressed, 
  subequal, 
  the 
  branchial 
  siphon 
  larger, 
  and 
  ciliated 
  at 
  the 
  

   orifice. 
  Foot 
  small, 
  compressed, 
  linguiform. 
  Labial 
  appendages 
  long, 
  

   narrow, 
  pointed, 
  and 
  triangular." 
  

  

  Lucinopsis. 
  — 
  As 
  no 
  very 
  complete 
  description 
  of 
  the 
  animal 
  of 
  this 
  

   genus 
  has 
  been 
  published, 
  I 
  give 
  the 
  following 
  from 
  observation 
  of 
  

   Torbay 
  specimens: 
  — 
  Animal 
  suborbicular, 
  mantle 
  closed, 
  except 
  for 
  

   a 
  small 
  foot-opening, 
  margins 
  smooth. 
  The 
  foot 
  is 
  small, 
  laterally 
  

   compressed, 
  and 
  broadly 
  attached 
  to 
  the 
  body 
  ; 
  it 
  does 
  not 
  show 
  any 
  

   byssal 
  groove. 
  The 
  siphons 
  are 
  very 
  long, 
  entirely 
  separate, 
  divergent, 
  

  

  1 
  Cat. 
  Bivalve 
  Shells 
  in 
  Brit. 
  Mus., 
  pt. 
  ii, 
  p. 
  217, 
  1854. 
  

  

  