﻿STRUCTURE 
  AND 
  CLASSIFICATION 
  OF 
  THE 
  AHAOHNIDA. 
  239 
  

  

  inhabiting 
  sandy 
  deserts 
  form 
  extensive 
  burrows. 
  The 
  fifth 
  

   pair 
  of 
  prosomatic 
  appendages 
  is 
  used 
  by 
  these 
  scorpions 
  

   Avheu 
  burrowing 
  to 
  kick 
  back 
  the 
  sand 
  as 
  the 
  burrow 
  is 
  

   excavated 
  by 
  the 
  great 
  chelas. 
  

  

  References 
  to 
  works 
  dealing 
  with 
  the 
  taxonomy 
  and 
  geo- 
  

   graphical 
  distribution 
  of 
  scorpions 
  are 
  given 
  at 
  the 
  end 
  of 
  

   this 
  article 
  (28) 
  . 
  

  

  Section 
  /3. 
  Epectiuata. 
  — 
  The 
  primitive 
  distinction 
  be- 
  

   tween 
  the 
  mesosoma 
  and 
  the 
  metasoma 
  wholly 
  or 
  almost 
  

   wholly 
  obliterated^ 
  the 
  two 
  regions 
  uniting 
  to 
  form 
  an 
  

   opisthosoma, 
  which 
  never 
  consists 
  of 
  more 
  than 
  twelve 
  somites 
  

   and 
  never 
  bears 
  appendages 
  or 
  breathing 
  organs 
  behind 
  the 
  

   fourth 
  somite. 
  The 
  breathing 
  organs 
  of 
  the 
  opisthosomaj 
  

   when 
  present, 
  represented 
  by 
  two 
  pairs 
  of 
  stigmata, 
  opening 
  

   either 
  upon 
  the 
  first 
  and 
  second 
  (Pedipalpi) 
  or 
  the 
  second 
  

   and 
  third 
  somites 
  (Solifugte, 
  pseudo-Scorpiones), 
  or 
  by 
  a 
  

   single 
  pair 
  upon 
  the 
  third 
  (? 
  second) 
  somite 
  (Opiliones) 
  of 
  the 
  

   opisthosoma, 
  there 
  being 
  rarely 
  an 
  additional 
  stigma 
  on 
  the 
  

   fourth 
  {some 
  Solifugae). 
  The 
  appendages 
  of 
  the 
  second 
  

   somite 
  of 
  the 
  opisthosoma 
  absent, 
  rarely 
  minute 
  and 
  bud-like 
  

   (some 
  Amblypygi), 
  never 
  pectiniform. 
  A 
  prasgenital 
  somite 
  

   is 
  often 
  present 
  either 
  in 
  a 
  reduced 
  condition 
  forming 
  a 
  

   waist 
  (Pedipalpi, 
  Aranese, 
  Palpigradi) 
  or 
  as 
  a 
  full-sized 
  

   tergal 
  plate 
  (pseudo-Scorpiones) 
  ; 
  in 
  some 
  it 
  is 
  entirely 
  atro- 
  

   phied 
  (Solifugae, 
  Holosomata, 
  and 
  Rhynchostomi). 
  Lateral 
  

   eyes, 
  when 
  present, 
  diplostichous. 
  

  

  Remarks. 
  — 
  The 
  epectinate 
  Arachnids 
  do 
  not 
  stand 
  so 
  

   close 
  to 
  the 
  aquatic 
  ancestors 
  of 
  the 
  Embolubranchia 
  as 
  do 
  the 
  

   pectiniferous 
  scorpions. 
  At 
  the 
  same 
  time 
  we 
  are 
  not 
  justified 
  

   in 
  supposing 
  that 
  the 
  scorpions 
  stand 
  in 
  any 
  way 
  as 
  an 
  inter- 
  

   mediate 
  grade 
  between 
  any 
  of 
  the 
  existing 
  Epectinata 
  and 
  

   the 
  Delobranchia. 
  It 
  is 
  probable 
  that 
  the 
  Pedipalpi, 
  Araneee, 
  

   and 
  Podogona 
  have 
  been 
  separately 
  evolved 
  as 
  distinct 
  lines 
  

   of 
  descent 
  from 
  the 
  ancient 
  aquatic 
  Arachnida. 
  TheHoloso- 
  

   mata 
  and 
  Rhynchostomi 
  are 
  pi'obably 
  offshoots 
  from 
  the 
  

   stem 
  of 
  the 
  Aranete, 
  and 
  it 
  is 
  not 
  unlikely 
  (in 
  view 
  of 
  the 
  

   structure 
  of 
  the 
  prosomatic 
  somites 
  of 
  the 
  Tartarides) 
  that 
  

  

  