﻿122 
  PROCHEDINGS 
  OF 
  THE 
  MALACOLOGICAL 
  SOCIETY. 
  

  

  (C) 
  Shell 
  light 
  yellowish-brown, 
  excepting 
  for 
  a 
  pale 
  unpigmented 
  

   zone 
  round 
  the 
  periphery. 
  Specimens 
  intermediate 
  in 
  colour 
  

   between 
  this 
  and 
  the 
  last 
  mutation 
  are 
  not 
  very 
  rare, 
  but 
  a 
  careful 
  

   examination 
  of 
  a 
  large 
  number 
  of 
  individuals 
  supports 
  the 
  view 
  that 
  

   the 
  two 
  mutations 
  will 
  probably 
  prove 
  to 
  be 
  distinct. 
  About 
  half 
  

   the 
  specimens 
  found 
  in 
  IJevonshire 
  belong 
  to 
  this 
  form, 
  and 
  it 
  is 
  not 
  

   uucommon 
  on 
  the 
  Continent. 
  Moquin-Tandon 
  probably 
  united 
  this 
  

   and 
  the 
  last 
  luutation 
  in 
  his 
  var. 
  sarratina^ 
  (if 
  one 
  is 
  right 
  in 
  

   assuming 
  that 
  the 
  last 
  also 
  occurs 
  in 
  France), 
  and 
  this 
  name 
  might 
  

   therefore 
  be 
  given 
  to 
  the 
  vast 
  majority 
  of 
  the 
  English 
  examples. 
  

  

  (D) 
  Shell 
  unpigmented 
  excepting 
  for 
  a 
  brown 
  band 
  just 
  above 
  

   tlie 
  periphery. 
  This 
  mutation, 
  which 
  has 
  been 
  figured 
  by 
  Hidalgo,- 
  

   occurs 
  in 
  many 
  localities 
  on 
  the 
  Continent, 
  although 
  it 
  is 
  a 
  little 
  

   scarcer 
  than 
  the 
  last. 
  Specimens 
  having 
  the 
  opaque 
  white 
  band 
  in 
  

   addition 
  to 
  the 
  brown 
  one 
  were 
  named 
  xav. 
  ferussina 
  by 
  Moquin- 
  

   Tandon^; 
  perhaps, 
  however, 
  this 
  name 
  might 
  be 
  applied 
  also 
  to 
  those 
  

   less 
  frequent 
  examples 
  which 
  are 
  without 
  the 
  opaque 
  band. 
  

  

  (E) 
  Shell 
  entirely 
  unpigmented, 
  being 
  white 
  beneath 
  a 
  pale 
  

   greenisli-yellow 
  periostracum 
  ; 
  animal 
  pigmented, 
  but 
  usually 
  of 
  

   a 
  rather 
  lighter 
  colour 
  than 
  in 
  the 
  case 
  of 
  those 
  with 
  brown 
  shells. 
  

   This 
  is 
  the 
  most 
  abundant 
  mutation 
  in 
  France, 
  and 
  those 
  specimens 
  

   which 
  have 
  the 
  opaque 
  peripheral 
  band, 
  and 
  which 
  are 
  the 
  

   commonest, 
  constitute 
  the 
  typical 
  form 
  of 
  the 
  species. 
  In 
  Haute 
  

   Garonne 
  about 
  60 
  per 
  cent, 
  of 
  the 
  specimens 
  appear 
  to 
  belong 
  to 
  this 
  

   mutation 
  and 
  only 
  about 
  8 
  per 
  cent, 
  to 
  the 
  last.* 
  Ferussac 
  states 
  

   that 
  all 
  intermediate 
  stages 
  occur 
  between 
  these 
  pale 
  yellowish- 
  

   white 
  shells 
  and 
  those 
  belonging 
  to 
  the 
  brown 
  mutations,^ 
  but 
  such 
  

   intermediate 
  shells 
  are 
  not 
  common. 
  

  

  (F) 
  Shell 
  and 
  animal 
  both 
  unpigmented. 
  Some 
  of 
  the 
  Devonshire 
  

   shells 
  resemble 
  tliose 
  belonging 
  to 
  the 
  last 
  mutation 
  in 
  being 
  

   unpigmented, 
  but 
  Mr. 
  Kennard 
  assures 
  me 
  that 
  in 
  them 
  the 
  animal 
  

   as 
  well 
  as 
  the 
  shell 
  is 
  always 
  white. 
  They 
  must, 
  therefore, 
  belong 
  

   to 
  a 
  distinct 
  mutation, 
  which 
  may 
  be 
  the 
  var. 
  cdbina, 
  Moq., 
  although 
  

   in 
  his 
  original 
  description 
  of 
  this 
  variety 
  Moquin-Tandon 
  does 
  not 
  

   mention 
  that 
  the 
  animal 
  is 
  white 
  as 
  well 
  as 
  the 
  shell. 
  

  

  Foot, 
  Hkad, 
  and 
  Neck. 
  — 
  The 
  foot 
  is 
  long, 
  rather 
  narrow, 
  and 
  

   bluntly 
  pointed 
  at 
  the 
  hinder 
  end. 
  There 
  is 
  no 
  caudal 
  mucous 
  pore. 
  

   The 
  sole 
  is 
  undivided 
  by 
  longitudinal 
  grooves. 
  The 
  foot-fringe 
  is 
  

   crossed 
  by 
  transverse 
  grooves, 
  but 
  it 
  is 
  ill-defined, 
  owing 
  to 
  the 
  

   absence 
  of 
  any 
  peripodial 
  grooves. 
  A 
  median 
  groove 
  runs 
  along 
  the 
  

   top 
  of 
  the 
  posterior 
  part 
  of 
  the 
  foot, 
  which 
  is 
  very 
  obtusely 
  keeled. 
  

   Paired 
  dorsal 
  and 
  oblique 
  lateral 
  grooves 
  appear 
  on 
  the 
  neck, 
  but 
  

   they 
  are 
  not 
  conspicuously 
  differentiated 
  from 
  the 
  general 
  network 
  

   of 
  grooves 
  which 
  divides 
  the 
  skin 
  into 
  numerous 
  small 
  ruga) 
  

  

  1 
  Hist. 
  Nat. 
  des 
  Moll. 
  terr. 
  et 
  fluv. 
  de 
  France, 
  vol. 
  ii, 
  1856, 
  p. 
  194. 
  

  

  2 
  Cat. 
  Moll. 
  terr. 
  Espana 
  Port, 
  y 
  los 
  Baleares, 
  pi. 
  xxiii, 
  figs. 
  243-5. 
  

   2 
  Op. 
  cit., 
  p. 
  194. 
  

  

  * 
  Ibid., 
  p. 
  196. 
  

  

  * 
  Hist. 
  Nat. 
  des 
  Moll. 
  terr. 
  et 
  fluv., 
  vol. 
  i, 
  p. 
  201. 
  

  

  