﻿120 
  

  

  NOTES 
  ON 
  HYGROMIA 
  LIMB 
  AT 
  A 
  (DRAr.). 
  

  

  By 
  Hugh 
  Watson. 
  

  

  Read 
  14th 
  March, 
  1919. 
  

  

  PLATES 
  II 
  AND 
  III. 
  

  

  Hygromia 
  LiMBATA 
  Las 
  ouly 
  recently 
  been 
  found 
  to 
  be 
  indigenous 
  

   to 
  the 
  British 
  Isles/ 
  and 
  does 
  not 
  seem 
  to 
  be 
  at 
  all 
  well 
  known 
  to 
  

   English 
  malacologists 
  ; 
  it 
  is 
  therefore 
  hoped 
  that 
  the 
  following 
  notes 
  

   on 
  this 
  species 
  may 
  be 
  of 
  some 
  interest. 
  They 
  are 
  founded 
  chiefly 
  

   upon 
  an 
  examination 
  of 
  material 
  collected 
  in 
  Devonshire, 
  for 
  which 
  

   the 
  writer 
  is 
  deeply 
  indebted 
  to 
  Mr. 
  A. 
  S. 
  Ivennard, 
  who 
  first 
  

   discovered 
  the 
  shell 
  in 
  that 
  count3^ 
  

  

  NoMENCLA-XDRE. 
  — 
  It 
  has 
  recently 
  been 
  suggested 
  that, 
  since 
  Da 
  Costa 
  

   nsed 
  the 
  name 
  Helix 
  limhata 
  for 
  a 
  Plmiorbis 
  before 
  Draparnaud 
  gave 
  

   the 
  same 
  name 
  to 
  this 
  species, 
  Draparuaud's 
  name 
  should 
  be 
  discarded 
  

   and 
  odeca 
  used 
  in 
  its 
  stead 
  ; 
  but 
  this 
  course 
  has 
  not 
  been 
  adopted 
  by 
  

   the 
  writer, 
  because 
  he 
  is 
  doubtful 
  whether 
  the 
  form 
  named 
  odeca 
  by 
  

   Bourguigaat 
  and 
  Locard 
  is 
  identical 
  witli 
  the 
  present 
  species, 
  and 
  he 
  

   questions 
  the 
  desirability 
  of 
  discarding 
  well-known 
  names 
  on 
  purely 
  

   technical 
  grounds. 
  

  

  Size. 
  — 
  The 
  average 
  height 
  of 
  the 
  shell 
  in 
  the 
  Devonshire 
  locality 
  

   seems 
  to 
  be 
  about 
  8'4 
  mm., 
  and 
  the 
  average 
  breadth 
  about 
  12*1 
  mm. 
  

   Among 
  twenty 
  full-grown 
  specimens 
  the 
  two 
  largest 
  measured 
  

   9*3x13 
  mm., 
  while 
  the 
  smallest 
  was 
  only 
  7'3 
  X 
  11*1 
  mm. 
  Specimens 
  

   from 
  France 
  and 
  the 
  North 
  of 
  Spain 
  are 
  usually 
  somewhat 
  larger 
  

   than 
  this, 
  though 
  varying 
  considerably 
  in 
  size. 
  The 
  two 
  smallest 
  

   examples 
  that 
  the 
  writer 
  found 
  at 
  Pau, 
  Basses- 
  Pyrenees, 
  measure 
  

   7'6xll'7mm. 
  and 
  8xll'3mm. 
  ; 
  while 
  the 
  two 
  largest 
  in 
  his 
  

   collection, 
  from 
  Salies-de-Bearu 
  in 
  the 
  same 
  Department, 
  are 
  no 
  less 
  

   than 
  11 
  X 
  16'4 
  mm. 
  and 
  13x16 
  mm. 
  respectivelv. 
  

  

  Form 
  of 
  Shell. 
  (PL 
  III, 
  figs. 
  12, 
  13, 
  17-19.)— 
  The 
  shell 
  is 
  

   sub-globose, 
  and 
  iisually 
  somewhat 
  depressed, 
  although 
  the 
  height 
  of 
  

   the 
  spire 
  varies. 
  The 
  most 
  depressed 
  shell 
  among 
  the 
  twenty 
  

   Devonshire 
  specimens 
  measures 
  8xl2"5mm., 
  and 
  the 
  most 
  conical 
  

   9xl2'2mm. 
  ; 
  but 
  the 
  writer 
  has 
  examples 
  from 
  Salies-de-Bearn 
  

   varying 
  from 
  lO'lxlo'omm. 
  to 
  ll"3xl3mm. 
  (figs. 
  18 
  and 
  19). 
  

   The 
  last 
  specimen, 
  however, 
  is 
  ver_y 
  unusually 
  conical 
  for 
  the 
  species, 
  

   and 
  should 
  probably 
  be 
  placed 
  in 
  the 
  variety 
  trochoides, 
  Moq. 
  On 
  an 
  

   average 
  the 
  height 
  of 
  the 
  shell 
  is 
  probably 
  about 
  70 
  per 
  cent, 
  of 
  its 
  

   breadth 
  in 
  both 
  English 
  and 
  Freucli 
  specimens 
  of 
  the 
  species. 
  

  

  The 
  number 
  of 
  whorls 
  in 
  the 
  Devonshire 
  examples 
  is 
  usuallj' 
  

   between 
  5^ 
  and 
  5J, 
  but 
  some 
  of 
  the 
  largest 
  of 
  the 
  Continental 
  shells 
  

   have 
  as 
  many 
  as 
  ^\ 
  whorls. 
  Young 
  shells 
  are 
  keeled, 
  but 
  the 
  angle 
  

   disappears 
  completely 
  in 
  the 
  course 
  of 
  the 
  last 
  whorl. 
  Above 
  the 
  

   periphery 
  the 
  whorls 
  are 
  slightly 
  flattened, 
  below 
  it 
  they 
  are 
  more 
  

   convex. 
  The 
  suture 
  is 
  shallow, 
  the 
  umbilicus 
  deep 
  but 
  very 
  narrow, 
  

  

  ^ 
  Kennard 
  i& 
  Woodward, 
  Proc. 
  Malac. 
  Soc, 
  vol. 
  xiii, 
  1918, 
  pp. 
  14, 
  15. 
  

  

  