﻿422 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.86 
  

  

  Postpectus. 
  — 
  The 
  incurved 
  part 
  of 
  mesosternum 
  anterior 
  to 
  middle 
  

   coxae, 
  frequently 
  defined 
  by 
  transverse 
  carinate 
  extensions 
  of 
  the 
  

   carinae 
  that 
  flank 
  the 
  coxal 
  foramina 
  (pi. 
  52, 
  figs. 
  36-38, 
  40, 
  42). 
  

  

  Postpectoral 
  carina. 
  — 
  The 
  carina 
  defining 
  the 
  postpectus. 
  

  

  Pronotal 
  sinus. 
  — 
  A 
  cleft 
  in 
  the 
  humeral 
  angle 
  of 
  pronotum 
  between 
  

   the 
  humeral 
  angle 
  itself 
  and 
  the 
  flange 
  by 
  which 
  the 
  pronotum 
  is 
  

   attached 
  to 
  mesopleuron. 
  In 
  Ophion 
  and 
  Thyreodon 
  the 
  sinus 
  is 
  

   broad, 
  exposing 
  the 
  spiracular 
  sclerite, 
  whereas 
  in 
  Enicospilus 
  it 
  is 
  

   narrow 
  and 
  the 
  spiracular 
  sclerite 
  is 
  hidden 
  by 
  the 
  humeral 
  angle 
  

   (pi. 
  55, 
  figs. 
  72-74). 
  

  

  Spiracular 
  sclerite. 
  — 
  A 
  small, 
  free 
  sclerite 
  between 
  the 
  base 
  of 
  the 
  

   tegula 
  and 
  the 
  humeral 
  angle 
  of 
  the 
  pronotum, 
  sometimes 
  concealed 
  

   by 
  the 
  latter 
  (pi. 
  55, 
  figs. 
  72-74). 
  

  

  Transverse 
  brace. 
  — 
  The 
  combined 
  intercubitus, 
  second 
  abscissa 
  of 
  

   cubitus 
  and 
  second 
  recurrent 
  vein. 
  The 
  comparative 
  lengths 
  of 
  

   these 
  elements 
  is 
  stated 
  as 
  a 
  ratio, 
  e. 
  g., 
  1:2:4, 
  the 
  figures 
  represent- 
  

   ing 
  the 
  veins 
  in 
  the 
  same 
  order 
  as 
  mentioned 
  above 
  (pi. 
  53, 
  fig. 
  52). 
  

  

  Umbo 
  of 
  second 
  tergite. 
  — 
  A 
  median, 
  convex, 
  polished 
  articulating 
  

   area 
  at 
  base 
  of 
  second 
  tergite 
  set 
  off 
  laterally 
  by 
  pits 
  and 
  usuaUy 
  

   dorsally 
  by 
  a 
  constriction 
  or 
  impression. 
  It 
  is 
  characteristic 
  of 
  the 
  

   Ophion 
  group 
  of 
  genera 
  and 
  undeveloped 
  in 
  the 
  Enicospilus 
  and 
  

   Thyreodon 
  groups 
  (pi. 
  56, 
  figs. 
  94-99). 
  

  

  Tribe 
  OPHIONINI 
  

  

  GROUP 
  CHARACTERS 
  AND 
  GENERIC 
  CHARACTERS 
  

  

  In 
  order 
  to 
  construct 
  a 
  key 
  placing 
  the 
  genera 
  in 
  as 
  near 
  their 
  

   natural 
  relationship 
  as 
  possible 
  it 
  has 
  been 
  necessary 
  in 
  most 
  cases 
  

   to 
  employ 
  groups 
  of 
  characters 
  rather 
  than 
  single 
  characters. 
  A 
  vast 
  

   majority 
  of 
  the 
  species 
  of 
  the 
  tribe 
  belong 
  to 
  the 
  genera 
  Ophion, 
  

   Enicospilus, 
  and 
  Thyreodon, 
  and 
  the 
  principal 
  couplets, 
  Nos. 
  1 
  and 
  

   7, 
  of 
  the 
  key 
  embody 
  the 
  most 
  significant 
  characters 
  distinguishing 
  

   typical 
  members 
  of 
  those 
  genera. 
  Although 
  the 
  characters 
  in 
  couplet 
  

   7 
  are 
  stated 
  positively, 
  not 
  all 
  the 
  genera 
  or, 
  indeed, 
  all 
  species 
  of 
  

   the 
  basic 
  genera 
  agree 
  with 
  all 
  the 
  characters 
  applying 
  to 
  the 
  cate- 
  

   gories 
  in 
  which 
  they 
  belong. 
  Agreement 
  with 
  a 
  majority 
  of 
  the 
  

   characters 
  in 
  either 
  alternate 
  determines 
  the 
  subsequent 
  course 
  of 
  a 
  

   specimen 
  through 
  the 
  key. 
  

  

  Very 
  few 
  of 
  the 
  characters 
  employed 
  in 
  the 
  key 
  are 
  peculiar 
  to 
  

   single 
  genera 
  or 
  even 
  to 
  single 
  groups 
  of 
  genera. 
  The 
  anomalous 
  

   hind 
  claws 
  (pi. 
  55, 
  fig. 
  77) 
  and 
  frenulum 
  (pi. 
  54, 
  fig. 
  56) 
  of 
  Spilophion, 
  

   the 
  notched 
  apical 
  front 
  tarsal 
  joint 
  of 
  Ophiogastrella 
  (pi. 
  55, 
  fig. 
  75), 
  

   and 
  the 
  remarkably 
  long 
  and 
  slender 
  Hgula 
  of 
  Agathophiona 
  (pi. 
  50, 
  

   fig. 
  28) 
  apparently 
  occur 
  in 
  no 
  other 
  genus, 
  and 
  are 
  of 
  themselves 
  

   diagnostic. 
  

  

  