﻿Watson: 
  notes 
  on 
  nYGiiosiiA 
  limbata 
  {d^kv.). 
  129 
  

  

  spermatheca, 
  and 
  in 
  the 
  undivided 
  niesocoues 
  of 
  its 
  marginal 
  teeth. 
  

   In 
  all 
  these 
  features 
  Hygromia 
  limbata 
  (Drap.) 
  agrees 
  more 
  closely 
  

   with 
  H. 
  fusca 
  (Mont.), 
  which 
  is 
  certainl}' 
  its 
  nearest 
  ally 
  in 
  tlie 
  

   British 
  fauna. 
  Nevertheless, 
  //. 
  fusca 
  (Mont.) 
  could 
  never 
  be 
  

   mistaken 
  for 
  H. 
  limbata 
  (Drap.) 
  on 
  account 
  of 
  the 
  much 
  smaller, 
  

   extremely 
  thin 
  shell 
  of 
  the 
  former 
  species. 
  

  

  Hygromia 
  incarnata 
  (Miill.), 
  a 
  species 
  which 
  is 
  very 
  common 
  in 
  

   Central 
  Europe 
  and 
  the 
  North-East 
  of 
  France, 
  bears 
  a 
  much 
  closer 
  

   resemblance 
  to 
  II. 
  limbata 
  (Drap.) 
  than 
  do 
  any 
  of 
  the 
  British 
  

   species 
  (see 
  pi. 
  Ill, 
  fig. 
  14); 
  and 
  if 
  it 
  should 
  find 
  its 
  way 
  into 
  

   England, 
  as 
  II. 
  umbrosa 
  (Partsch) 
  has 
  already 
  done, 
  it 
  might 
  easily 
  

   be 
  mistaken 
  for 
  U. 
  limbata, 
  var. 
  sarratina, 
  Moq. 
  The 
  shell 
  of 
  

   II. 
  incarnata 
  (Miill.) 
  differs, 
  however, 
  from 
  that 
  of 
  H. 
  limbata 
  (Dra-p.) 
  

   in 
  the 
  whorls 
  being 
  slightly 
  more 
  rounded, 
  the 
  aperture 
  a 
  little 
  

   smaller 
  and 
  less 
  oblique, 
  the 
  outer 
  lip 
  slightly 
  thickei', 
  tlie 
  columellar 
  

   lip 
  less 
  nearly 
  vertical, 
  the 
  umbilicus 
  not 
  quite 
  so 
  narrow, 
  and 
  the 
  

   surface 
  slightly 
  less 
  glossy, 
  owing 
  to 
  the 
  microscopical 
  granulation 
  

   being 
  much 
  coarser 
  than 
  in 
  II. 
  limbata 
  (Drap.), 
  as 
  will 
  be 
  seen 
  on 
  

   comparing 
  figs. 
  22 
  and 
  26. 
  Internally 
  H. 
  incarnata 
  (Miill.) 
  differs 
  

   from 
  H. 
  limbata 
  (Drap.) 
  in 
  the 
  undivided 
  mesocones 
  of 
  its 
  marginal 
  

   teeth 
  (pi. 
  Ill, 
  fig. 
  31), 
  as 
  well 
  as 
  in 
  the 
  form 
  of 
  its 
  spermatheca, 
  

   dart-sac, 
  etc' 
  

  

  In 
  its 
  general 
  anatomy 
  II. 
  cinctella 
  (Drap.), 
  the 
  type 
  of 
  the 
  genus 
  

   Hygromia, 
  agrees 
  much 
  more 
  closely 
  with 
  H. 
  limbata 
  (Di'ap.) 
  than 
  

   does 
  either 
  H. 
  incarnata 
  (Miill.) 
  or 
  H. 
  ftisca 
  (Mont.). 
  The 
  shell 
  of 
  

   H. 
  cinctella 
  (Drap.) 
  can 
  easily 
  be 
  distinguished 
  from 
  that 
  of 
  an 
  

   adult 
  H. 
  limbata 
  (Drap.) 
  bj^ 
  its 
  more 
  pronounced 
  keel, 
  and 
  by 
  its 
  

   simple, 
  scarcely 
  expanded, 
  outer 
  lip; 
  but 
  it 
  is 
  easy 
  to 
  mistake 
  

   a 
  specimen 
  of 
  II. 
  cinctella 
  (Drap 
  ) 
  for 
  a 
  young 
  example 
  of 
  H. 
  limbata 
  

   (Drap.). 
  It 
  will 
  be 
  seen, 
  liowever, 
  from 
  figs. 
  15-17 
  that 
  a 
  young 
  

   H. 
  limbata 
  (Drap.) 
  has 
  a 
  more 
  globular 
  shell 
  with 
  a 
  narrower 
  mouth, 
  

   H. 
  cinctella 
  (Drap.) 
  being 
  more 
  pyramidal 
  in 
  form. 
  JMoreover, 
  the 
  

   microscopical 
  sculpture 
  of 
  tlie 
  shells 
  is 
  slightly 
  different, 
  the 
  minute 
  

   ridges 
  being 
  longer, 
  narrower, 
  and 
  less 
  developed 
  in 
  H. 
  cinctella 
  

   (Drap.), 
  in 
  fact 
  not 
  quite 
  so 
  unlike 
  ordinary 
  lines 
  of 
  growtli 
  

   (pi. 
  Ill, 
  fig. 
  23). 
  The 
  jaw 
  of 
  H. 
  cinctella 
  (Drap.) 
  is 
  slightly 
  

   larger 
  than 
  that 
  of 
  H. 
  limbata 
  (Drap.), 
  notwithstanding 
  that 
  the 
  

   shell 
  is 
  a 
  little 
  smaller, 
  and 
  the 
  folds 
  upon 
  it 
  are 
  nearly 
  obsolete 
  

   (pi. 
  Ill, 
  fig. 
  28). 
  The 
  marginal 
  teeth 
  of 
  the 
  radula 
  have 
  bifid 
  

   mesocones, 
  but 
  the 
  ectocones 
  of 
  the 
  lateral 
  teeth 
  are 
  more 
  distinct 
  

   than 
  in 
  H. 
  limbata 
  (Drap.), 
  and 
  all 
  the 
  teeth 
  are 
  rather 
  shorter 
  

   (pi. 
  Ill, 
  fig. 
  30). 
  The 
  reproductive 
  organs 
  are 
  of 
  the 
  same 
  general 
  

   type 
  as 
  in 
  H. 
  limbata 
  (Drap.), 
  (pi. 
  Ill, 
  fig. 
  21); 
  but 
  the 
  terminal 
  

   enlargement 
  of 
  the 
  .spermatheca 
  has 
  not 
  entirely 
  disappeared, 
  the 
  

   epiphallus 
  is 
  not 
  quite 
  so 
  long, 
  the 
  dart-sac 
  is 
  slightly 
  more 
  prominent, 
  

   and 
  the 
  penis 
  and 
  vagina 
  are 
  both 
  slightly 
  shorter 
  and 
  broader, 
  

  

  ' 
  See 
  Schmidt, 
  " 
  Der 
  Gescblechtsapparat 
  der 
  Stylommatopboren 
  " 
  : 
  Abhandl. 
  

   Naturwiss. 
  Vereines 
  fur 
  Sacbsen 
  und 
  Thiiringen 
  in 
  Halle, 
  vol. 
  i, 
  1855, 
  

   pi. 
  v, 
  fig. 
  25. 
  

  

  