﻿128 
  

  

  PKOCEICDINGS 
  OF 
  THU 
  MALACOLOGICAL 
  SOCIETr. 
  

  

  one 
  time. 
  Unless 
  otherwise 
  stated, 
  the 
  following 
  refers 
  to 
  specimens 
  

   judged 
  to 
  be 
  mature 
  in 
  this 
  way. 
  

  

  Of 
  317 
  specimens, 
  184 
  (58 
  per 
  cent) 
  were 
  males 
  and 
  133 
  (42 
  per 
  cent) 
  

   females. 
  

  

  I. 
  Altitudk 
  and 
  Diameter. 
  

  

  "The 
  altitudes 
  and 
  diameters, 
  distributed 
  in 
  convenient 
  groups 
  of 
  

   0'3 
  mm., 
  are 
  shown 
  in 
  the 
  table, 
  which 
  gives 
  also 
  the 
  relation 
  between 
  

   altitude 
  and 
  diameter 
  for 
  each 
  group. 
  

  

  "13 
  + 
  6"= 
  13 
  males, 
  6 
  females. 
  

  

  Further 
  analysis 
  of 
  these 
  figures 
  gives 
  the 
  following 
  summary 
  

   results 
  : 
  — 
  

  

  Altitude 
  mm. 
  

  

  Max. 
  Min. 
  Mean. 
  

  

  Males 
  . 
  14-5 
  12-1 
  13-21 
  

  

  Females 
  . 
  loS 
  13-2 
  14-36 
  

  

  Total 
  . 
  15-8 
  12-1 
  13-69 
  

  

  Males 
  

  

  Females 
  

  

  Total 
  

  

  10-3 
  

   11-4 
  

   11-4 
  

  

  Diameter 
  mm. 
  

   8-6 
  9-44 
  

  

  9-2 
  10-26 
  

  

  8-6 
  9-78 
  

  

  It 
  is 
  clear 
  from 
  these 
  results 
  ' 
  that 
  the 
  females 
  are 
  definitely 
  larger 
  

   than 
  the 
  males. 
  Of 
  the 
  males 
  77 
  of 
  184 
  (42 
  per 
  cent) 
  are 
  smaller 
  (in 
  

   altitude) 
  than 
  the 
  smallest 
  female, 
  and 
  of 
  the 
  females 
  47 
  of 
  133 
  

  

  For 
  statistical 
  methods 
  and 
  the 
  interpretation 
  of 
  the 
  results 
  1 
  have 
  followed 
  

   G. 
  U. 
  Yule, 
  Introduction 
  to 
  the 
  Study 
  of 
  Statistics 
  (2nd 
  ed., 
  London, 
  1912), 
  

   where 
  a 
  plain 
  account 
  of 
  the 
  methods 
  of 
  testing 
  the 
  validity 
  of 
  numerical 
  

   differences 
  will 
  be 
  found. 
  

  

  