﻿12 
  JOURNAL 
  OF 
  the; 
  WASHINGTON 
  ACADEMY 
  OF* 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  1 
  

  

  centrus 
  hitherto 
  has 
  been 
  the 
  only 
  Teleost 
  known 
  in 
  which 
  there 
  is 
  a 
  

   true 
  spiral 
  valve 
  in 
  the 
  adult. 
  

  

  The 
  stomach 
  of 
  Argentina 
  silus 
  is 
  siphon-shaped, 
  somewhat 
  like 
  

   that 
  of 
  a 
  salmon, 
  although 
  the 
  posterior 
  end-curve 
  is 
  conical, 
  suggest- 
  

   ing 
  a 
  short 
  caecum. 
  The 
  pyloric 
  limb 
  is 
  the 
  shorter, 
  being 
  about 
  

   half 
  the 
  length 
  of 
  the 
  cardiac 
  limb. 
  

  

  The 
  duodenum, 
  as 
  it 
  extends 
  forward, 
  curves 
  downward 
  and 
  then 
  

   upward. 
  It 
  then 
  passes 
  to 
  one 
  side 
  of 
  the 
  stomach 
  near 
  the 
  median 
  

   line. 
  In 
  the 
  specimen 
  from 
  which 
  the 
  drawing 
  was 
  made 
  (Fig. 
  1), 
  

   there 
  were 
  twenty-five 
  pyloric 
  caeca. 
  Just 
  posterior 
  to 
  the 
  stomach, 
  

   the 
  intestine 
  bends 
  sharply 
  upward 
  and 
  transversely, 
  then 
  backward, 
  

   after 
  which 
  it 
  runs 
  in 
  a 
  straight 
  line 
  to 
  the 
  anal 
  opening. 
  This 
  part 
  

   of 
  the 
  intestine 
  is 
  occupied 
  by 
  a 
  well-developed, 
  though 
  simply 
  con- 
  

   structed, 
  spiral 
  valve 
  (Fig. 
  lA). 
  The 
  exterior 
  shows 
  eighteen 
  or 
  

   twenty 
  transverse 
  septa 
  on 
  a 
  little 
  over 
  two-thirds 
  the 
  length 
  of 
  the 
  

   straight 
  part 
  of 
  the 
  intestine, 
  but 
  there 
  are 
  several 
  incomplete 
  whorls 
  

   at 
  the 
  anterior 
  end 
  and 
  a 
  few 
  closely 
  folded 
  ones 
  at 
  the 
  posterior 
  end 
  

   which 
  do 
  not 
  show 
  externally. 
  Back 
  of 
  the 
  spiral 
  valve, 
  the 
  intestine 
  

   is 
  a 
  straight 
  tube. 
  

  

  A 
  specimen 
  ^^ 
  of 
  young 
  Argentina 
  silus 
  49 
  mm. 
  long 
  shows 
  a 
  well- 
  

   developed 
  spiral 
  valve. 
  

  

  The 
  air 
  bladder 
  is 
  thick-walled 
  and 
  silvery, 
  with 
  a 
  small 
  aperture 
  

   in 
  the 
  posterior 
  end 
  which 
  suggests 
  a 
  pneumatic 
  duct 
  connection 
  

   but 
  which 
  could 
  not 
  be 
  traced. 
  

  

  SOME 
  SKELETAL 
  CHARACTERISTICS 
  

  

  Cranium.- 
  — 
  ^The 
  most 
  prominent 
  feature 
  in 
  a 
  dorsal 
  view 
  of 
  the 
  

   cranium 
  is 
  the 
  large 
  frontal 
  bones 
  which 
  extend 
  backward 
  above 
  the 
  

   eyes 
  and 
  nearly 
  to 
  the 
  posterior 
  margin 
  of 
  the 
  cranium, 
  almost 
  com- 
  

   pletely 
  covering 
  the 
  parietals. 
  The 
  frontals 
  overlap 
  each 
  other 
  and 
  

   they 
  are 
  so 
  closely 
  bound 
  together 
  that 
  it 
  is 
  difficult 
  to 
  separate 
  them. 
  

   When 
  they 
  are 
  removed, 
  the 
  thin 
  and 
  rather 
  narrow 
  parietals 
  are 
  

   seen 
  lapped 
  underneath 
  these 
  bones. 
  The 
  parietals 
  overlap 
  each 
  

   other 
  widely 
  and 
  also 
  cover 
  the 
  supraoccipital 
  except 
  for 
  the 
  supra- 
  

   occipital 
  crest 
  and 
  a 
  narrow 
  posterior 
  margin. 
  The 
  supraoccipital 
  

   bone 
  is 
  extended 
  foreward 
  into 
  a 
  tongue-shaped 
  process 
  upon 
  which 
  

   the 
  parietals 
  rest. 
  This 
  process 
  is 
  connected 
  by 
  a 
  cartilaginous 
  bridge 
  

  

  " 
  In 
  the 
  collection 
  of 
  Mr. 
  W. 
  W. 
  Welsh, 
  U. 
  S. 
  Bureau 
  of 
  Fisheries. 
  Grampus 
  station 
  

   10027. 
  August 
  14, 
  1912. 
  

  

  