﻿JAN. 
  4, 
  1922 
  KENDALL 
  AND 
  CRAWFORD: 
  ARGENTINA 
  SILUS 
  

  

  15 
  

  

  upward 
  posterior 
  to 
  the 
  stylus, 
  while 
  in 
  Osmerus 
  this 
  is 
  not 
  the 
  case. 
  

   (Fig. 
  2, 
  D.) 
  

  

  Pelvic 
  Bones. 
  — 
  The 
  pelvic 
  bones 
  differ 
  widely 
  from 
  those 
  of 
  other 
  

   Isospondyli. 
  There 
  is 
  one 
  distal 
  pterygiophore 
  loosely 
  articulated 
  

   to 
  the 
  basipterygium. 
  Above 
  it, 
  there 
  is 
  a 
  large, 
  spheroidal 
  swelling 
  

   of 
  hard 
  bone 
  excavated 
  on 
  the 
  inner 
  side 
  to 
  which 
  the 
  first 
  ray 
  is 
  

   articulated. 
  From 
  this 
  spheroidal 
  swelling, 
  a 
  slender 
  shaft 
  projects 
  

  

  A 
  

  

  3 
  

  

  V 
  

  

  Fig. 
  2. 
  A, 
  basipterigium 
  of 
  Argentina 
  silus, 
  X 
  IVal 
  B, 
  basipterigium 
  of 
  Osmenus 
  

   mordax, 
  X 
  3; 
  C, 
  basipterygium 
  of 
  Salmo 
  sehago, 
  X 
  2; 
  D, 
  caudal 
  vertebrae 
  of 
  

   Argentina 
  silus, 
  X 
  2; 
  E, 
  45th 
  vertebrae 
  of 
  Argentina 
  silus, 
  showing 
  the 
  arched 
  

   connection 
  between 
  the 
  haemopophyses, 
  X 
  2. 
  

  

  forward 
  along 
  the 
  margin 
  and 
  another 
  shaft, 
  originating 
  at 
  the 
  base 
  

   of 
  the 
  first, 
  runs 
  diagonally 
  forward 
  across 
  the 
  basipterygium. 
  The 
  

   anterior 
  margin 
  of 
  the 
  basipterygium 
  extends 
  diagonally 
  across 
  the 
  

   ends 
  of 
  the 
  two 
  shafts, 
  the 
  whole 
  bone 
  being 
  trapezoidal 
  in 
  shape, 
  

   as 
  shown 
  in 
  figure 
  2, 
  A. 
  In 
  this 
  respect, 
  it 
  differs 
  from 
  the 
  basip- 
  

   terygia 
  of 
  other 
  Isospondyli 
  which 
  are 
  roughly 
  triangular 
  in 
  outline. 
  

   (Fig. 
  2, 
  B, 
  C.) 
  A 
  lateral 
  process 
  extends 
  inward 
  to 
  meet 
  a 
  similar 
  

   process 
  on 
  the 
  opposite 
  side. 
  

  

  Pectoral 
  Girdle. 
  — 
  There 
  is 
  no 
  postclavical 
  such 
  as 
  that 
  found 
  in 
  

   a 
  salmonid. 
  The 
  actinosts 
  are 
  thin, 
  but 
  they 
  are 
  connected 
  by 
  webs 
  

   of 
  bone. 
  The 
  mesocoracoid 
  is 
  present 
  and 
  well 
  developed. 
  The 
  

   supratemporal 
  is 
  a 
  thin, 
  blade-shaped 
  bone 
  loosely 
  attached 
  to 
  the 
  

   upper 
  posterior 
  margin 
  of 
  the 
  supraoccipital. 
  Of 
  the 
  two 
  processes 
  

   of 
  the 
  posttemporal 
  bone, 
  the 
  lower 
  which 
  curves 
  downward 
  is 
  the 
  

  

  