﻿410 
  Mr. 
  Frederick 
  Muir 
  on 
  the 
  

  

  Figure 
  1 
  represents 
  in 
  a 
  semidiagrammatic 
  manner 
  the 
  

   skeleton 
  of 
  the 
  male 
  genitaha 
  of 
  Rhynchojihornsferruginevs. 
  

   The 
  seventh 
  tergite 
  is 
  large 
  and 
  forms 
  the 
  pygidium, 
  its 
  

   apical 
  margin 
  meets 
  the 
  apical 
  margin 
  of 
  the 
  seventh 
  

   sternite 
  and 
  closes 
  the 
  outer 
  cloaca. 
  The 
  eighth 
  tergite 
  

   is 
  much 
  smaller 
  and 
  fits 
  into 
  the 
  convexity 
  of 
  the 
  ventral 
  

   side 
  of 
  the 
  seventh 
  tergite, 
  to 
  which 
  it 
  is 
  connected 
  by 
  a 
  

   large 
  membrane 
  allowing 
  of 
  considerable 
  play. 
  The 
  basal 
  

   margin 
  of 
  the 
  eighth 
  tergite 
  is 
  produced 
  into 
  two 
  large, 
  

   flat 
  processes 
  or 
  struts 
  to 
  which 
  the 
  protractor 
  muscles 
  

   are 
  attached 
  and 
  allow 
  of 
  greater 
  play. 
  The 
  eighth 
  sternite 
  

   is 
  small 
  and 
  together 
  with 
  the 
  eighth 
  tergite 
  closes 
  the 
  

   inner 
  cloaca. 
  The 
  apical 
  margins 
  of 
  the 
  eighth 
  segment 
  is 
  

   connected 
  to 
  the 
  base 
  of 
  the 
  tegmen 
  by 
  a 
  large 
  membrane 
  

   {im 
  1 
  and 
  ptg), 
  the 
  median 
  portion 
  of 
  which 
  is 
  chitinised 
  

   and 
  forms 
  the 
  pseudotegmen. 
  At 
  the 
  base 
  where 
  it 
  joins 
  

   the 
  eighth 
  segment 
  this 
  membrane 
  forms 
  a 
  narrow 
  tube 
  

   (shown 
  too 
  large 
  in 
  the 
  figure), 
  which 
  allows 
  of 
  the 
  median 
  

   lobe 
  moving 
  through 
  it 
  but 
  does 
  not 
  admit 
  of 
  any 
  lateral 
  

   motion. 
  The 
  anus 
  {an) 
  opens 
  on 
  the 
  membrane 
  beneath 
  the 
  

   eighth 
  tergite. 
  The 
  tegmen 
  consists 
  of 
  a 
  strong 
  chitinous 
  

   ring 
  {tr), 
  incomplete 
  on 
  the 
  dorsal 
  area 
  where 
  the 
  chitin 
  

   curves 
  shghtly 
  apically 
  but 
  does 
  not 
  meet, 
  and 
  a 
  large, 
  

   strong 
  strut 
  {tgs) 
  which 
  varies 
  somewhat 
  in 
  shape 
  and 
  size 
  

   in 
  different 
  specimens, 
  the 
  one 
  figured 
  (1 
  a) 
  being 
  large 
  and 
  

   broad 
  at 
  the 
  apex; 
  a 
  strong 
  keel 
  runs 
  down 
  the 
  dorsal 
  

   surface 
  of 
  the 
  strut. 
  The 
  median 
  layer 
  or 
  median 
  tube 
  

   consists 
  of 
  the 
  median 
  lobe 
  and 
  the 
  membrane 
  connecting 
  

   it 
  to 
  the 
  tegmen. 
  The 
  median 
  lobe 
  is 
  a 
  tube 
  incompletely 
  

   chitinised, 
  the 
  ventral 
  plate 
  being 
  nearly 
  divided 
  into 
  three 
  

   pieces 
  by 
  two 
  deep, 
  narrow 
  membranous 
  areas 
  ; 
  the 
  basal 
  

   corners 
  of 
  the 
  ventral 
  plate 
  are 
  continued 
  as 
  two 
  narrow 
  

   struts 
  {ms) 
  ; 
  the 
  dorsal 
  plate 
  is 
  produced 
  basad 
  farther 
  

   than 
  the 
  ventral 
  plate. 
  The 
  median 
  struts 
  {ms) 
  at 
  first 
  form 
  

   chitinisations 
  on 
  the 
  surface 
  of 
  the 
  median 
  lobe 
  and 
  later 
  

   join 
  the 
  invaginations 
  which 
  form 
  the 
  free 
  struts. 
  The 
  

   internal 
  sac 
  (is) 
  lies 
  within 
  the 
  median 
  lobe. 
  

  

  The 
  chief 
  muscles 
  which 
  control 
  the 
  movements 
  of 
  this 
  

   skeleton 
  are 
  (fig. 
  2) 
  : 
  — 
  

  

  {a) 
  Retractor 
  and 
  protractor 
  muscles 
  from 
  the 
  pseudo- 
  

   tegmen 
  to 
  the 
  eighth 
  segment, 
  by 
  which 
  the 
  pseudotegmen 
  

   is 
  held 
  firmly 
  in 
  its 
  place 
  and 
  moved 
  through 
  a 
  limited 
  

   distance. 
  

  

  (6) 
  A 
  large 
  series 
  of 
  muscles 
  from 
  the 
  apex 
  of 
  the 
  pseudo- 
  

  

  