﻿14 
  Mr. 
  R. 
  I. 
  Pocock 
  on 
  the 
  

  

  with 
  smaller, 
  more 
  squamiform 
  tubercles. 
  In 
  small 
  speci- 
  

   mens 
  the 
  tubercles 
  are 
  scarcely 
  perceptible. 
  The 
  relative 
  

   thickness 
  of 
  the 
  segment 
  varies 
  much 
  ; 
  in 
  one 
  large 
  specimen 
  

   its 
  upper 
  surface 
  is 
  very 
  convex 
  from 
  behind 
  forwards, 
  and 
  

   the 
  thickness 
  is 
  almost 
  equal 
  to 
  a 
  third 
  of 
  its 
  length. 
  From 
  

   this 
  extreme 
  there 
  is 
  every 
  intermediate 
  step 
  until 
  the 
  thick- 
  

   ness 
  becomes 
  less 
  than 
  one 
  fifth 
  of 
  the 
  length. 
  The 
  carpus 
  

   is 
  a 
  little 
  shorter 
  than 
  the 
  propodus 
  when 
  measured 
  along 
  

   their 
  external 
  surfaces 
  ; 
  both 
  are 
  covered 
  with 
  smooth, 
  

   rounded 
  or 
  flattened, 
  scattered 
  or 
  close-set 
  tubercles, 
  the 
  

   inferior 
  flattened 
  surface 
  of 
  the 
  carpus 
  alone 
  being 
  without 
  

   tubercles. 
  Upper 
  surface 
  of 
  the 
  carpus 
  produced 
  distally 
  into 
  

   an 
  evenly 
  rounded 
  process 
  which 
  overhangs 
  the 
  proximal 
  end 
  

   of 
  the 
  propodus; 
  inferior 
  half 
  of 
  propodus 
  somewhat 
  com- 
  

   pressed. 
  In 
  small 
  specimens 
  the 
  tubercles 
  may 
  be 
  completely 
  

   spiniform, 
  and 
  some 
  of 
  them 
  show 
  a 
  remarkable 
  development 
  

   of 
  these 
  spines 
  at 
  the 
  end 
  of 
  the 
  propodus. 
  Dactylus 
  short, 
  

   less 
  than 
  a 
  third 
  the 
  length 
  of 
  the 
  propodus, 
  spined 
  beneath, 
  

   bearing 
  a 
  sharp 
  claw. 
  The 
  carpus 
  and 
  propodus 
  are 
  more 
  

   cylindrical 
  and 
  relatively 
  more 
  slender 
  in 
  small 
  individuals. 
  

  

  The 
  two 
  succeeding 
  pereiopods 
  much 
  resemble 
  that 
  which 
  

   has 
  been 
  just 
  described, 
  except 
  that 
  they 
  are 
  smaller 
  and' 
  

   differ 
  with 
  regard 
  to 
  the 
  relative 
  length 
  of 
  their 
  segments. 
  

  

  The 
  ischio-merus 
  of 
  the 
  fifth 
  is 
  shorter 
  than 
  that 
  of 
  the 
  

   fourth, 
  and 
  the 
  fourth 
  shorter 
  than 
  that 
  of 
  the 
  third. 
  The 
  

   carpal 
  segments, 
  however, 
  vary 
  considerably 
  in 
  length 
  ; 
  thus, 
  

   they 
  may 
  present 
  in 
  larger 
  forms 
  the 
  same 
  relative 
  size 
  as 
  the 
  

   ischio-meral 
  segments, 
  or 
  they 
  may 
  in 
  smaller 
  forms 
  be 
  equal 
  

   in 
  the 
  three 
  pairs 
  of 
  appendages. 
  The 
  propodus, 
  on 
  the 
  con- 
  

   trary, 
  of 
  the 
  fifth 
  pair 
  is 
  always 
  longer 
  than 
  those 
  of 
  the 
  other 
  

   two, 
  and 
  the 
  propodus 
  of 
  the 
  fourth 
  may 
  be 
  either 
  equal 
  to, 
  

   less 
  than, 
  or 
  greater 
  than 
  that 
  of 
  the 
  third. 
  The 
  external 
  

   surface 
  of 
  each 
  of 
  the 
  ischio-meral 
  segments 
  is 
  furnished 
  dis- 
  

   tally 
  with 
  a 
  small 
  rounded 
  prominence, 
  which 
  may 
  or 
  may 
  

   not 
  be 
  armed 
  with 
  two 
  or 
  three 
  small 
  spines; 
  the 
  under 
  sur- 
  

   face 
  of 
  this 
  segment 
  in 
  the 
  fourth 
  and 
  fifth 
  pairs 
  is 
  armed 
  

   with 
  an 
  oblique 
  series 
  of 
  three 
  or 
  four 
  larger 
  spines, 
  which 
  

   are 
  naturally 
  more 
  visible 
  in 
  smaller 
  specimens 
  in 
  which 
  the 
  

   tubercles 
  are 
  inconspicuous 
  or 
  absent, 
  but 
  more 
  or 
  fewer 
  of 
  

   them 
  may 
  have 
  entirely 
  disappeared 
  in 
  the 
  largest 
  specimens, 
  

   probably 
  having 
  been 
  converted 
  by 
  wear 
  into 
  tubercles. 
  

   That 
  the 
  squamiform 
  or 
  tuberculiform 
  armature 
  of 
  the 
  largest 
  

   specimens 
  has 
  been 
  derived 
  from 
  the 
  spiniform 
  armature 
  of 
  

   the 
  smaller 
  specimens 
  during 
  the 
  growth 
  of 
  the 
  individual 
  

   by 
  some 
  such 
  process 
  as 
  rubbing 
  seems 
  certain 
  from 
  the 
  

   frequent 
  occurrence 
  side 
  by 
  side 
  in 
  the 
  same 
  segment 
  in 
  larger 
  

  

  