﻿STRUCTUEK 
  AND 
  CLASSIFICATION 
  OF 
  THE 
  AEACHNIDA. 
  233 
  

  

  pectones 
  respectively, 
  those 
  of 
  the 
  third, 
  fourth, 
  fifth, 
  and 
  

   sixth 
  somites 
  (? 
  in 
  Palseophonus) 
  sinking 
  below 
  the 
  surface 
  

   during 
  growth 
  in 
  connection 
  with 
  the 
  formation 
  of 
  the 
  four 
  

   pairs 
  of 
  pulmonary 
  sacs 
  (see 
  Fig. 
  17). 
  Lateral 
  eyes 
  mono- 
  

   stichous. 
  

  

  Pig. 
  48. 
  

  

  Fig. 
  49. 
  

  

  Tig. 
  48. 
  — 
  Dorsal 
  view 
  of 
  a 
  restoration 
  of 
  Palseophonus 
  

   11 
  unci 
  us, 
  Tliorell, 
  the 
  Silurian 
  Scorpion 
  from 
  Gothland. 
  (Re- 
  

   stored 
  after 
  ThorcU's 
  indications 
  bj 
  Mr. 
  11. 
  I. 
  Pocock.) 
  

  

  Pig. 
  49. 
  — 
  Ventral 
  view 
  of 
  a 
  restoration 
  of 
  Palseopliouus 
  

   Huntcri, 
  Pocock, 
  the 
  Silurian 
  Scorpion 
  from 
  Lcsmahago, 
  Scot- 
  

   laud, 
  llestored 
  by 
  Mr. 
  Pt. 
  I. 
  Pocock. 
  Tiie 
  meeting 
  of 
  the 
  coxai 
  of 
  

   all 
  the 
  prosomatic 
  limbs 
  in 
  front 
  of 
  the 
  pentagonal 
  sternum 
  ; 
  the 
  

   space 
  for 
  a 
  genital 
  operculum 
  ; 
  the 
  pair 
  of 
  pecteus, 
  and 
  the 
  

   absence 
  of 
  any 
  evidence 
  of 
  pulmonary 
  stigmata 
  are 
  noticeable 
  in 
  

   this 
  specimen. 
  (See 
  Pocock,' 
  Quart. 
  Journ. 
  Micr. 
  Sci.,' 
  1901.) 
  

  

  Order 
  i. 
  Scorpionidea. 
  — 
  Prosoma 
  covered 
  by 
  a 
  single 
  dorsal 
  

   shield, 
  bearing 
  typically 
  median 
  and 
  lateral 
  eyes; 
  its 
  sternal 
  

   elements 
  reduced 
  to 
  a 
  single 
  plate 
  lodged 
  between 
  or 
  behind 
  

  

  