﻿362 
  MARGERY 
  MOSELEY. 
  

  

  the 
  various 
  kinds. 
  The 
  native 
  A. 
  pall 
  i 
  pes 
  of 
  the 
  Thames 
  

   was 
  for 
  many 
  years 
  used 
  ab 
  Oxford, 
  but 
  within 
  the 
  last 
  twenty 
  

   years 
  it 
  has 
  become 
  rare 
  in 
  the 
  Thames 
  owing 
  to 
  a 
  disease 
  of 
  

   the 
  gills, 
  and 
  finer 
  examples 
  are 
  now 
  supplied 
  by 
  London 
  

   dealers. 
  These 
  most 
  frequently 
  consist 
  of 
  French 
  specimens, 
  

   ecrevissesa 
  puttes 
  rouges, 
  the 
  true 
  Astacusfluviatilis, 
  

   Fabr. 
  On 
  examining 
  a 
  specimen 
  of 
  the 
  true 
  A. 
  fluviatilis 
  in 
  

   the 
  Oxford 
  laboratory, 
  I 
  observed 
  a 
  minute 
  rudimentary 
  gill 
  

   in 
  a 
  position 
  which 
  appeared 
  to 
  correspond 
  to 
  the 
  arthrodial 
  

   membrane 
  of 
  Somite 
  VII 
  (that 
  of 
  the 
  first 
  pair 
  of 
  maxillipeds). 
  

   I 
  give 
  a 
  more 
  detailed 
  account 
  of 
  this 
  rudimentary 
  gill 
  

   below 
  ; 
  here 
  I 
  wish 
  to 
  point 
  out 
  especially 
  the 
  very 
  curious 
  

   fact 
  that 
  this 
  anterior 
  rudimentary 
  gill 
  is 
  not 
  present 
  in 
  

   A. 
  torrentium, 
  A. 
  pallipes, 
  or 
  A. 
  leptodactylus, 
  but 
  it 
  

   is 
  present 
  on 
  both 
  sides 
  in 
  every 
  specimen 
  of 
  true 
  A. 
  

   fluviatilis 
  which 
  I 
  have 
  examined. 
  These 
  amount 
  to 
  about 
  

   thirty, 
  varying 
  in 
  size 
  from 
  3^ 
  inches 
  to 
  44 
  inches 
  from 
  the 
  tip 
  of 
  

   the 
  rostrum 
  to 
  the 
  end 
  of 
  the 
  telson. 
  It 
  thus 
  becomes 
  a 
  specific 
  

   character 
  of 
  A. 
  fluviatilis, 
  and 
  the 
  fact 
  that 
  it 
  is 
  not 
  present 
  

   in 
  the 
  smaller 
  and 
  larger 
  species 
  allied 
  to 
  A. 
  fluviatilis 
  goes 
  

   some 
  way 
  towards 
  explaining 
  how 
  it 
  was 
  that 
  it 
  escaped 
  the 
  

   observation 
  of 
  Professor 
  Huxley, 
  and 
  that 
  Oxford 
  was 
  for 
  

   many 
  years 
  supplied 
  with 
  A. 
  pallipes 
  explains 
  Avhy 
  it 
  was 
  

   not 
  found 
  in 
  the 
  Oxford 
  laboratory 
  before. 
  

  

  I 
  have 
  been 
  enabled 
  to 
  examine 
  a 
  number 
  of 
  specimens 
  of 
  

   exotic 
  species 
  of 
  Astacidse 
  belonging 
  to 
  the 
  Natural 
  History 
  

   Museum, 
  South 
  Kensington, 
  by 
  the 
  kindness 
  of 
  Professor 
  

   Lankester, 
  and 
  have 
  not 
  discovered 
  in 
  them 
  the 
  new 
  rudi- 
  

   mentary 
  anterior 
  gill. 
  However, 
  in 
  a 
  male 
  specimen 
  ofAstacus 
  

   dauricus^ 
  from 
  Corea, 
  of 
  length 
  b^ 
  centimetres 
  from 
  tip 
  of 
  

   rostrum 
  to 
  end 
  of 
  telson, 
  on 
  the 
  right 
  side 
  and 
  in 
  exactly 
  the 
  

   same 
  position 
  as 
  the 
  new 
  rudiment 
  in 
  A. 
  fluviatilis 
  there 
  was 
  

   a 
  minute 
  papilla, 
  just 
  visible 
  to 
  the 
  naked 
  eye, 
  of 
  length 
  ^ 
  milli- 
  

   metre. 
  This 
  is 
  the 
  only 
  specimen 
  of 
  A. 
  dauricus 
  which 
  I 
  have 
  

   examined, 
  and 
  on 
  the 
  left 
  side, 
  which 
  I 
  looked 
  at 
  first, 
  I 
  could 
  

  

  ' 
  Specimens 
  iu 
  the 
  Museum 
  collection 
  are 
  so 
  labelled. 
  More 
  probably, 
  

   however, 
  they 
  are 
  A. 
  (Gambaroides) 
  similis, 
  Koelbel. 
  (W. 
  T, 
  C.) 
  

  

  