﻿346 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.44. 
  

  

  larger 
  stigma) 
  it 
  is 
  convex; 
  in 
  BiareoUna 
  neglecta 
  it 
  is 
  conspicuously 
  

   angulate 
  or 
  subdentata 
  about 
  the 
  middle. 
  

  

  Libellulapis 
  wilmattx 
  is 
  easily 
  known 
  from 
  L. 
  antiquorum 
  by 
  its 
  

   much 
  larger 
  size. 
  

  

  Habitat. 
  — 
  Miocene 
  shales 
  of 
  Florissant, 
  at 
  Wilson's 
  ranch; 
  col- 
  

   lected 
  July, 
  1912, 
  by 
  Wilmatte 
  P. 
  Cockerell. 
  

  

  Holotype.—C&t. 
  No. 
  58688, 
  U.S.N.M. 
  

  

  Family 
  CEPHID.E. 
  

   Genus 
  JANUS 
  Stephens. 
  

  

  JANUS 
  DISPERDITUS, 
  new 
  species. 
  

  

  Length 
  13 
  mm., 
  but 
  apex 
  of 
  abdomen 
  (probably 
  1 
  mm.) 
  missing; 
  

   anterior 
  wing 
  8f 
  mm.; 
  width 
  of 
  abdomen 
  (flattened) 
  3^ 
  mm., 
  of 
  

   thorax 
  3 
  mm.; 
  the 
  head 
  was 
  apparently 
  black, 
  or 
  at 
  least 
  very 
  dark; 
  

   the 
  thorax 
  dark 
  brown, 
  but 
  paler 
  than 
  head; 
  the 
  abdomen 
  and 
  legs 
  

   apparently 
  ferruginous; 
  wings 
  clear, 
  with 
  ferruginous 
  nervures. 
  

  

  The 
  venation 
  of 
  anterior 
  wings 
  agrees 
  almost 
  exactly 
  with 
  Janus 
  

   integer, 
  as 
  represented 
  by 
  MacGillivray,^ 
  except 
  as 
  follows 
  : 
  

  

  (1 
  ) 
  The 
  veins 
  are 
  more 
  robust, 
  like 
  those 
  figured 
  by 
  MacGUlivray 
  for 
  

   J. 
  abhreviatus. 
  

  

  (2) 
  The 
  first 
  (basal) 
  marginal 
  cell 
  has 
  its 
  basal 
  corner 
  ver}^ 
  acute, 
  

   more 
  as 
  in 
  MacrocepJius. 
  

  

  (3) 
  The 
  first 
  recurrent 
  nervure 
  exactly 
  meets 
  the 
  first 
  traiisverso- 
  

   cubital, 
  also 
  as 
  in 
  MacrocejjTius. 
  

  

  (4) 
  The 
  second 
  recurrent 
  meets 
  the 
  second 
  transversocubital. 
  

  

  (5) 
  The 
  basal 
  nervure 
  on 
  first 
  submarginal 
  cell 
  is 
  shorter, 
  as 
  in 
  J. 
  

   abbreviatus. 
  (The 
  relative 
  positions 
  of 
  the 
  basal 
  and 
  transverso- 
  

   medial 
  nervures 
  are 
  exactly 
  as 
  in 
  J. 
  integer, 
  not 
  as 
  in 
  Macroc^phus) 
  . 
  

  

  (6) 
  The 
  stigma 
  is 
  formed 
  as 
  in 
  J. 
  abbreviatus. 
  (More 
  robust 
  than 
  

   in 
  Macrocephus) 
  . 
  

  

  (7) 
  The 
  third 
  submarginal 
  cell 
  is 
  verj 
  long, 
  longer 
  than 
  in 
  J. 
  integer, 
  

   and 
  quite 
  unlike 
  the 
  relatively 
  short 
  cell 
  of 
  Macrocephus. 
  The 
  

   following 
  measurements 
  are 
  m 
  microns 
  : 
  

  

  Second 
  submarginal 
  cell 
  on 
  lower 
  side 
  1, 
  232 
  

  

  Third 
  submarginal 
  cell 
  on 
  lower 
  side 
  1, 
  232 
  

  

  Third 
  submarginal 
  cell 
  on 
  apical 
  side 
  784 
  

  

  Third 
  submarginal 
  cell 
  on 
  upper 
  side 
  1, 
  072 
  

  

  What 
  can 
  be 
  seen 
  of 
  the 
  hmd 
  wing 
  seems 
  normal 
  for 
  the 
  genus, 
  but 
  

   the 
  apex 
  of 
  the 
  median 
  cell 
  (subcostal 
  of 
  Marlatt) 
  is 
  more 
  acute 
  than 
  

   in 
  J. 
  integer, 
  herem 
  rather 
  resembling 
  MacrocepTius. 
  

  

  Miocene 
  shales 
  of 
  Florissant; 
  1912. 
  Collected 
  by 
  W. 
  P. 
  Cockerell 
  

   at 
  the 
  Wilson 
  ranch. 
  This 
  is 
  the 
  first 
  fossil 
  cephid 
  from 
  America. 
  

   Among 
  the 
  European 
  fossils, 
  this 
  must 
  fall 
  nearest 
  to 
  Electrocephalus 
  

   strahlendorffl 
  Konow, 
  from 
  Baltic 
  Amber, 
  

  

  Type. 
  — 
  In 
  the 
  collections 
  in 
  the 
  University 
  of 
  Colorado. 
  

  

  iProc. 
  U. 
  S. 
  Nat. 
  Mus., 
  vol. 
  29, 
  pi. 
  43, 
  fig. 
  93. 
  

  

  