﻿dementia 
  subJiaphana, 
  Cavjy. 
  339 
  

  

  As 
  a 
  matter 
  of 
  fact, 
  the 
  shell 
  which 
  Carpenter 
  described, 
  

   but 
  did 
  not 
  figure, 
  was 
  the 
  young 
  of 
  this 
  species 
  and 
  liis 
  

   type 
  only 
  measured 
  three-quarters 
  of 
  an 
  inch 
  in 
  width, 
  with 
  

   a 
  very 
  thin 
  shell 
  ; 
  whereas 
  the 
  adult 
  is 
  over 
  two 
  inches 
  wide 
  

   and 
  is 
  not 
  particularly 
  thin. 
  It 
  seems 
  also 
  to 
  be 
  very 
  variable 
  

   in 
  shape, 
  for 
  Dr. 
  Dall 
  has 
  figured 
  a 
  variety 
  of 
  it 
  in 
  the 
  

   Proc. 
  U.S. 
  Nat. 
  Mus. 
  for 
  1891, 
  but 
  now 
  admits 
  that 
  this 
  

   was 
  " 
  an 
  exceptionally 
  rotund 
  specimen/^ 
  whereas 
  he 
  recog- 
  

   nizes 
  that 
  called 
  C 
  ohliqna 
  by 
  me 
  as 
  " 
  the 
  more 
  common 
  and 
  

   elongated 
  type 
  " 
  of 
  subdiaphana. 
  

  

  Through 
  the 
  kindness 
  of 
  Mr. 
  MacAndrew 
  I 
  have 
  been 
  able 
  

   to 
  examine 
  an 
  authentic 
  specimen 
  of 
  C. 
  subdiaphana, 
  and 
  am 
  

   satisfied 
  that 
  Dr. 
  Dall's 
  identification 
  is 
  correct, 
  and 
  that 
  

   C. 
  ob/iqua 
  must 
  be 
  regarded 
  as 
  a 
  synonym 
  of 
  C. 
  diaphuna. 
  

   The 
  published 
  figure, 
  however, 
  will 
  be 
  just 
  as 
  useful 
  as 
  if 
  it 
  

   were 
  that 
  of 
  a 
  new 
  species, 
  because 
  the 
  typical 
  form 
  of 
  the 
  

   shell 
  has 
  never 
  before 
  been 
  figured, 
  and 
  Mr. 
  E. 
  A. 
  Smith 
  

   informs 
  me 
  that 
  the 
  British 
  Museum 
  does 
  not 
  possess 
  an 
  

   adult 
  specimen 
  of 
  it 
  — 
  only 
  a 
  very 
  small 
  one 
  (5 
  mm. 
  across), 
  

   marked 
  as 
  named 
  from 
  the 
  type 
  specimens. 
  No 
  one 
  there- 
  

   fore 
  who 
  referred 
  to 
  this 
  example 
  in 
  the 
  National 
  Collection 
  

   would 
  imagine 
  that 
  it 
  grew 
  to 
  the 
  size 
  of 
  that 
  figured 
  by 
  me, 
  

   nor 
  would 
  he 
  suppose 
  it 
  to 
  be 
  the 
  same 
  species. 
  

  

  Lastly, 
  it 
  is 
  evident 
  that 
  the 
  specimens 
  on 
  which 
  T 
  founded 
  

   the 
  species 
  C. 
  obliqua 
  cannot 
  have 
  come 
  from 
  Poito 
  Rico 
  in 
  

   the 
  Caribbean, 
  but 
  must 
  have 
  been 
  obtained 
  from 
  some 
  place 
  

   on 
  the 
  western 
  coast 
  of 
  America, 
  where 
  C 
  subdiaphana 
  

   ranges 
  from 
  Alaska 
  in 
  the 
  north 
  to 
  California 
  in 
  the 
  south. 
  

   The 
  ticket 
  sold 
  with 
  these 
  specimens 
  must 
  have 
  belonged 
  to 
  

   some 
  other 
  shell 
  in 
  Mr. 
  Bulow^s 
  collection, 
  and 
  must 
  have 
  

   been 
  misplaced. 
  

  

  Doubt 
  has 
  been 
  thrown 
  on 
  the 
  propriety 
  of 
  referring 
  

   C. 
  subdiaphana 
  to 
  the 
  genus 
  dementia, 
  but 
  the 
  shell 
  really 
  

   does 
  not 
  differ 
  from 
  the 
  typical 
  species 
  {C. 
  papyracea) 
  more 
  

   than 
  does 
  C. 
  vatheleti, 
  which 
  was 
  figured 
  on 
  the 
  same 
  plate. 
  

   Its 
  chief 
  point 
  of 
  difference 
  is 
  the 
  absence 
  of 
  undulations 
  in 
  

   the 
  shell, 
  but 
  this 
  is 
  not 
  so 
  marked 
  a 
  difference 
  as 
  the 
  

   peculiar 
  surface-sculpturing 
  found 
  in 
  C. 
  granuJifera 
  and 
  

   C. 
  tasmanica, 
  which 
  do 
  seem 
  to 
  me 
  worthy 
  of 
  sectional 
  

   separation, 
  both 
  on 
  this 
  account 
  and 
  because 
  they 
  both 
  have 
  

   a 
  large 
  and 
  deep 
  pallial 
  sinus. 
  

  

  It 
  may 
  be 
  found 
  convenient 
  to 
  distinguish 
  C. 
  subdiaphana 
  

   and 
  C. 
  vatheleti 
  as 
  a 
  special 
  section 
  of 
  the 
  genus, 
  on 
  account 
  

   of 
  differences 
  in 
  the 
  animal, 
  but 
  I 
  maintain 
  that 
  they 
  should 
  

   still 
  be 
  retained 
  within 
  the 
  genus 
  dementia. 
  

  

  