﻿14 
  JOURNAL 
  OF 
  THE 
  WASHINGTON 
  ACADEMY 
  OE 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  1 
  

  

  tilage. 
  The 
  upper 
  and 
  outer 
  surface 
  of 
  this 
  bone 
  forms 
  a 
  broad 
  contact 
  

   with 
  the 
  inner 
  surface 
  of 
  the 
  articular. 
  The 
  articular 
  is 
  heavily 
  

   reenforced 
  on 
  the 
  inner 
  surface 
  at 
  its 
  articulation 
  with 
  the 
  quadrate. 
  

   The 
  angular 
  bone 
  is 
  present. 
  

  

  Vertebrae. 
  — 
  There 
  are 
  thirty-six 
  abdominal 
  and 
  thirty 
  caudal 
  vertebrae 
  

   in 
  the 
  vertebral 
  column 
  of 
  our 
  specimens 
  of 
  Argentina 
  silus}"^ 
  In 
  the 
  

   first 
  twenty-one 
  abdominal 
  vertebrae, 
  the 
  neurapophyses 
  are 
  not 
  fused 
  

   into 
  neural 
  spines 
  and 
  the 
  neural 
  canal 
  is 
  not 
  closed 
  above 
  in 
  the 
  

   first 
  twenty. 
  The 
  neural 
  canal 
  is 
  closed 
  in 
  the 
  twenty-first, 
  but 
  there 
  

   are 
  still 
  two 
  neural 
  spines. 
  The 
  parapophyses 
  of 
  the 
  abdominal 
  

   vertebrae 
  extend 
  outward 
  as 
  rather 
  broad, 
  rhomboidal 
  platforms 
  

   which 
  lie 
  nearly 
  horizontal, 
  the 
  ribs 
  being 
  attached 
  to 
  the 
  outer 
  

   corners. 
  The 
  parapophyses 
  become 
  progressively 
  narrower 
  poste- 
  

   riorly 
  and 
  gradually 
  merge 
  into 
  the 
  haemapophyses 
  of 
  the 
  caudal 
  

   vertebrae. 
  There 
  are 
  ribs 
  on 
  all 
  but 
  the 
  last 
  three 
  abdominal 
  para- 
  

   pophyses. 
  In 
  Salmo, 
  the 
  first 
  two 
  abdominal 
  vertebrae 
  do 
  not 
  bear 
  

   ribs. 
  

  

  Kpipleurals 
  are 
  borne 
  on 
  at 
  least 
  twenty-six 
  of 
  the 
  abdominal 
  

   vertebrae. 
  These 
  bones 
  are 
  ankylosed 
  with 
  the 
  neural 
  spines 
  and 
  

   may 
  not 
  be 
  separated 
  from 
  them 
  without 
  breaking 
  them 
  apart. 
  The 
  

   neurapophyses 
  of 
  these 
  vertebrae 
  are 
  articulated 
  loosely 
  to 
  the 
  centra 
  

   and 
  each 
  may 
  be 
  lifted 
  off 
  of 
  the 
  centrum 
  with 
  the 
  attached 
  zyga- 
  

   pophysis 
  and 
  epineural. 
  In 
  those 
  vertebrae 
  which 
  do 
  not 
  bear 
  epineu- 
  

   rals, 
  the 
  neurapophyses 
  are 
  ankylosed 
  with 
  the 
  centrum. 
  None 
  

   of 
  the 
  epipleurals 
  of 
  Salmo 
  or 
  Osmerus 
  are 
  ankylosed 
  with 
  the 
  neura- 
  

   pophyses. 
  

  

  In 
  the 
  caudal 
  vertebrae, 
  the 
  haemal 
  arch 
  is 
  closed, 
  but 
  in 
  the 
  first 
  

   nine, 
  the 
  haemapophyses 
  extend 
  downward 
  separately, 
  but 
  they 
  are 
  

   bridged 
  across 
  by 
  an 
  arch 
  instead 
  of 
  a 
  solid, 
  straight-edged 
  connection, 
  

   as 
  in 
  Salmo. 
  They 
  increase 
  in 
  length 
  posteriorly 
  and 
  taper 
  inward 
  

   toward 
  each 
  other 
  until, 
  in 
  the 
  tenth, 
  there 
  is 
  a 
  single 
  haemal 
  spine. 
  

   The 
  45th 
  vertebra 
  is 
  shown 
  in 
  figure 
  2, 
  E. 
  The 
  last 
  undoubted 
  

   vertebra 
  is 
  much 
  like 
  that 
  of 
  Osmerus. 
  The 
  caudal 
  stylus 
  is 
  composed 
  

   of 
  elements 
  extending 
  from 
  the 
  upper 
  and 
  lower 
  sides 
  of 
  the 
  centrum 
  

   whose 
  axis 
  is 
  directed 
  slightly 
  upward. 
  The 
  upper 
  element 
  of 
  the 
  

   stylus 
  is 
  the 
  heavier, 
  while 
  the 
  reverse 
  is 
  true 
  in 
  Osmerus. 
  However, 
  

   there 
  are 
  three 
  rather 
  indistinct 
  vertebrae 
  whose 
  axes 
  are 
  directed 
  

  

  " 
  The 
  following 
  numbers 
  of 
  vertebrae 
  in 
  Argentina 
  situs 
  are 
  recorded 
  in 
  various 
  ich- 
  

   thyological 
  works: 
  Day, 
  65; 
  Smitt, 
  65-68; 
  A. 
  Schubberg, 
  66. 
  

  

  