﻿16 
  PK0CKEDIN6S 
  OF 
  THK 
  M 
  ALACOLOGICAL 
  SOCIETY. 
  

  

  acuminate 
  behind, 
  white 
  with 
  a 
  few 
  remote 
  brown 
  marks 
  on 
  the 
  

   dorsal 
  margins 
  both 
  in 
  front 
  and 
  behind 
  the 
  umbones 
  ; 
  both 
  dorsal 
  

   margins 
  only 
  slightly 
  oblique, 
  ventral 
  margin 
  little 
  arcuate 
  in 
  the 
  

   middle, 
  but 
  curving 
  upward 
  at 
  both 
  ends; 
  valves 
  thin, 
  sculptured 
  

   with 
  fine 
  growth- 
  lines, 
  crossed 
  bj' 
  fine 
  threads 
  which 
  radiate 
  from 
  

   the 
  umbones, 
  the 
  thread 
  towards 
  the 
  hinder 
  end 
  being 
  more 
  distinct 
  

   than 
  those 
  in 
  front; 
  upon 
  the 
  posterior 
  excessively 
  fine 
  striae 
  are 
  

   observable 
  which 
  curve 
  from 
  the 
  margin 
  towards 
  the 
  other 
  radiating 
  

   threads 
  ; 
  umbones 
  brown 
  at 
  the 
  tip, 
  in 
  the 
  form 
  of 
  a 
  minute 
  glossy 
  

   boss 
  or 
  knob 
  of 
  a 
  difi'erent 
  texture 
  to 
  that 
  of 
  the 
  rest 
  of 
  the 
  shell 
  ; 
  

   interior 
  of 
  valves 
  glossy 
  white 
  ; 
  hinge-characters 
  normal 
  ; 
  pallial 
  sinus 
  

   tongue-like, 
  rounded 
  at 
  the 
  end, 
  not 
  reaching 
  quite 
  half-way 
  across 
  

   the 
  valves. 
  

  

  Length 
  8'5, 
  height 
  4"75, 
  diameter 
  3 
  mm. 
  

  

  This 
  species 
  resembles 
  P. 
  candidula, 
  Deshayes, 
  somewhat 
  in 
  form, 
  

   but 
  it 
  is 
  very 
  differently 
  sculptured. 
  The 
  generic 
  term 
  Gari 
  ' 
  of 
  

   tSchumacher 
  is 
  used 
  by 
  some 
  authors 
  as 
  being 
  anterior 
  to 
  Psammohia 
  

   of 
  Lamarck, 
  but 
  to 
  employ 
  a 
  word 
  with 
  a 
  genitive 
  termination 
  as 
  

   a 
  genus 
  hardly 
  seems 
  admissible. 
  

  

  Petricola. 
  digitai-e, 
  n.sp. 
  PI. 
  I, 
  Figs. 
  7, 
  8. 
  

  

  Shell 
  small, 
  sub-quadrate, 
  rather 
  convex 
  and 
  inequilateral, 
  white, 
  

   slightly 
  iridescent, 
  thin, 
  sculptured 
  with 
  excessively 
  fine 
  criss-ci^oss 
  

   raised 
  threads, 
  so 
  that 
  the 
  surface 
  presents 
  a 
  punctate 
  appearance 
  

   rather 
  like 
  a 
  thimble; 
  here 
  and 
  there 
  at 
  intervals 
  shallow 
  waves 
  of 
  

   growth 
  are 
  also 
  observable 
  ; 
  anterior 
  end 
  obtusely 
  rounded, 
  posterior 
  

   broader, 
  curvedly 
  sub-truncate, 
  ventral 
  margin 
  straightish, 
  not 
  much 
  

   curved 
  ; 
  anterior 
  dorsal 
  edge 
  oblique, 
  slightly 
  curved, 
  posterior 
  longer, 
  

   straighter, 
  less 
  descending 
  ; 
  lunular 
  area 
  large, 
  defined 
  by 
  a 
  distinct 
  

   curved 
  impressed 
  line 
  in 
  each 
  valve, 
  extending 
  from 
  the 
  umbo 
  to 
  the 
  

   ond 
  of 
  the 
  dorsal 
  slope 
  ; 
  the 
  surface, 
  unlike 
  the 
  rest 
  of 
  the 
  shell, 
  

   for 
  the 
  most 
  part 
  exhibits 
  little 
  punctation, 
  but 
  merely 
  the 
  most 
  

   delicate 
  growth-striae. 
  Umbones 
  raised 
  a 
  little 
  above 
  the 
  hinge- 
  

   margin, 
  contiguous, 
  smooth, 
  with 
  only 
  delicate 
  growth-strife 
  ; 
  three 
  

   cardinal 
  teeth 
  in 
  the 
  left 
  valve, 
  the 
  central 
  one 
  thick, 
  A-shaped, 
  the 
  

   others 
  oblique, 
  one 
  on 
  each 
  side 
  divergent 
  from 
  the 
  umbo 
  ; 
  right 
  valve 
  

   with 
  two 
  divergent 
  slender 
  teeth 
  which 
  fall, 
  when 
  the 
  shell 
  is 
  closed, 
  

   one 
  on 
  each 
  side 
  of 
  the 
  central 
  tooth 
  of 
  the 
  left 
  valve; 
  adductor 
  scars 
  

   large, 
  anterior 
  pyriform, 
  posterior 
  a 
  little 
  broader 
  ; 
  pallial 
  sinus 
  large, 
  

   broad, 
  ascending 
  high 
  and 
  beyond 
  the 
  middle 
  of 
  the 
  valve, 
  rounded 
  at 
  

   the 
  end; 
  liinge-ligament 
  occupying 
  about 
  half 
  the 
  posterior 
  dorsal 
  

   margin, 
  yellowish. 
  

  

  Length 
  6, 
  height 
  5'5, 
  diameter 
  4 
  mm. 
  

  

  This 
  shell 
  has 
  not 
  the 
  appearance 
  of 
  being 
  the 
  young 
  of 
  a 
  larger 
  

   form, 
  since 
  it 
  is 
  considerably 
  convex, 
  and 
  rather 
  like 
  certain 
  forms 
  of 
  

   Sphoivium 
  or 
  Kellia 
  in 
  general 
  aspect. 
  The 
  surface 
  to 
  the 
  naked 
  eye 
  

   appears 
  smooth, 
  and 
  the 
  punctate 
  or 
  thimble-like 
  appearance 
  of 
  the 
  

   surface 
  is 
  only 
  visible 
  under 
  a 
  lens. 
  

  

  ^ 
  From 
  the 
  Latin 
  garuni, 
  a 
  tish-sauce, 
  made 
  from 
  the 
  fish 
  garus. 
  

  

  