﻿24 
  PROCEEDINGS 
  OF 
  THE 
  MALACOLOGICAL 
  SOCIETY. 
  

  

  Probably 
  the 
  banding 
  is 
  a 
  primitive 
  character, 
  now 
  tending 
  to 
  

   disappear. 
  

  

  The 
  sculpture 
  varies 
  as 
  much 
  as 
  do 
  the 
  colour 
  bands. 
  It 
  may 
  be 
  

   said 
  that 
  there 
  are 
  three 
  general 
  types 
  of 
  sculpture. 
  0. 
  elrodi 
  (Pils.) 
  

   and 
  0. 
  idahoensis 
  (Newc.) 
  are 
  excellent 
  examples 
  of 
  a 
  type 
  with 
  very 
  

   strong 
  transverse 
  ribs. 
  0. 
  haydeni 
  (Gabb) 
  well 
  represents 
  a 
  type 
  

   with 
  very 
  strong 
  longitudinal 
  (spiral) 
  ribs. 
  Other 
  species 
  are 
  

   comparatively 
  smooth, 
  tliough 
  usually, 
  if 
  not 
  always, 
  really 
  repre- 
  

   senting 
  a 
  combination 
  of 
  the 
  characters 
  of 
  both 
  ribbed 
  types 
  on 
  

   a 
  reduced 
  scale. 
  Transversely 
  ribbed 
  forms 
  pass 
  by 
  minute 
  gradation 
  

   into 
  forms 
  with 
  numerous, 
  scarcely 
  noticeable 
  ribs 
  that 
  are 
  little 
  

   more 
  than 
  exaggerated 
  growth-lines. 
  Spirally 
  ribbed 
  forms 
  pass 
  

   into 
  those 
  in 
  which 
  the 
  spirals 
  may 
  be 
  detected 
  with 
  difficulty 
  by 
  aid 
  

   of 
  a 
  lens. 
  Such 
  as 
  cooperi 
  and 
  depressa 
  exhibit 
  more 
  or 
  less 
  indistinct 
  

   microscopic 
  spirals 
  ci'ossed 
  by 
  irregular, 
  somewhat 
  more 
  conspicuous 
  

   transverse 
  riblets. 
  

  

  The 
  relative 
  altitude 
  of 
  the 
  spire 
  in 
  certain 
  species, 
  if 
  not 
  in 
  all, 
  

   varies 
  greatly, 
  correlated 
  with 
  variation 
  in 
  relative 
  width 
  of 
  the 
  

   umbilicus. 
  It 
  has 
  been 
  suggested 
  that 
  this 
  might 
  be 
  due 
  to 
  

   environmental 
  conditions, 
  the 
  flatter 
  ones 
  being 
  better 
  able 
  to 
  hide 
  

   under 
  rocks 
  and 
  other 
  shelter, 
  and 
  hence 
  better 
  adapted 
  to 
  a 
  dry 
  

   habitat. 
  This 
  suggestion 
  seemed 
  to 
  me 
  plausible, 
  but 
  does 
  not 
  

   conform 
  to 
  the 
  facts 
  as 
  observed 
  in 
  the 
  field. 
  

  

  In 
  fact, 
  I 
  have 
  not 
  been 
  able 
  to 
  correlate 
  any 
  of 
  the 
  foregoing 
  

   variations 
  with 
  diiSerences 
  in 
  environment. 
  There 
  are 
  some 
  indica- 
  

   tions 
  that 
  unfavourable 
  environment 
  tends 
  to 
  dwarf 
  the 
  snails, 
  but 
  

   the 
  evidence 
  even 
  on 
  that 
  point 
  seems 
  inconclusive. 
  There 
  is 
  some 
  

   evidence 
  that 
  the 
  thickness 
  of 
  the 
  shell 
  is 
  directly 
  influenced 
  by 
  

   environmental 
  conditions, 
  but 
  further 
  investigation 
  is 
  desirable. 
  

  

  There 
  has 
  been 
  but 
  little 
  discussion 
  of 
  the 
  food 
  habits 
  of 
  these 
  

   snails. 
  I 
  liave 
  studied 
  a 
  number 
  of 
  flourishing 
  colonies 
  when 
  active. 
  

   Only 
  once 
  have 
  I 
  seen 
  them 
  feeding 
  on 
  green 
  vegetation. 
  They 
  

   were 
  then 
  eating 
  the 
  thick 
  leaves 
  of 
  Frasera 
  speciosa, 
  Griseb. 
  Once 
  

   or 
  twice 
  I 
  found 
  them 
  feeding 
  upon 
  live 
  bark 
  near 
  the 
  roots 
  of 
  

   shrubs. 
  With 
  those 
  exceptions, 
  I 
  have 
  not 
  found 
  green 
  leaves 
  or 
  

   bark 
  about 
  the 
  colonies 
  that 
  showed 
  slime 
  trails 
  or 
  looked 
  as 
  though 
  

   they 
  had 
  been 
  fed 
  upon 
  by 
  snails. 
  The 
  snails 
  were 
  almost 
  invariably 
  

   observed 
  upon 
  dead 
  leaves 
  and 
  decaying 
  wood, 
  apparently 
  feeding 
  

   upon 
  them, 
  or 
  possibly 
  upon 
  the 
  bacteria 
  of 
  decay 
  or 
  minute 
  fungi 
  on 
  

   them. 
  I 
  had 
  lioped 
  that 
  alcoholic 
  material 
  preserved 
  during 
  the 
  

   season 
  just 
  past 
  would 
  throw 
  some 
  light 
  upon 
  this 
  subject, 
  but 
  

   Professor 
  T. 
  D. 
  A. 
  Cockerell, 
  who 
  has 
  examined 
  some 
  of 
  it, 
  informs 
  

   me 
  that 
  they 
  contained 
  no 
  remains 
  of 
  food 
  at 
  all. 
  Since 
  the 
  snails 
  

   were 
  drowned 
  for 
  expansion 
  "before 
  scalding, 
  in 
  the 
  cleaning 
  process, 
  

   he 
  suggests 
  that 
  they 
  perhaps 
  expelled 
  all 
  food 
  during 
  the 
  process, 
  

   which 
  is 
  not 
  unlikely. 
  In 
  captivity 
  I 
  have 
  fed 
  them 
  with 
  lettuce, 
  

   cabbage, 
  and 
  other 
  vegetables, 
  and 
  have 
  been 
  informed 
  that 
  some 
  

   voraciously 
  ate 
  cornmeal. 
  I 
  have 
  seen 
  no 
  evidence 
  at 
  all 
  that 
  they 
  

   are 
  ever 
  carnivorous. 
  

  

  