﻿CHOKDKOSTEID^:. 
  27 
  

  

  in 
  its 
  sheath 
  ; 
  and 
  the 
  peripheral 
  arches 
  are 
  only 
  imperfectly 
  calci- 
  

   fied. 
  The 
  neural 
  arches 
  are 
  stout 
  and 
  each 
  pedicle 
  (PI. 
  I. 
  fig. 
  4, 
  

   n.a.) 
  is 
  separate 
  both 
  from 
  its 
  fellow 
  of 
  the 
  opposite 
  side 
  and 
  from 
  

   the 
  long 
  neural 
  spine 
  (n.s.). 
  No 
  traces 
  of 
  ribs 
  have 
  been 
  observed, 
  

   and 
  robust 
  haemal 
  arches 
  have 
  only 
  been 
  seen 
  at 
  the 
  base 
  of 
  the 
  

   lower 
  caudal 
  lobe. 
  

  

  The 
  pectoral 
  arch 
  closely 
  resembles 
  that 
  of 
  Acipenser. 
  The 
  post- 
  

   temporal 
  (figs. 
  3, 
  4, 
  p.t.) 
  is 
  a 
  small, 
  narrow 
  triangular 
  bone, 
  

   overlapped 
  at 
  its 
  attenuated 
  anterior 
  end 
  by 
  the 
  supratemporals. 
  

   The 
  long 
  narrow 
  supraclavicle 
  (figs. 
  3, 
  6, 
  s.cl.) 
  is 
  obliquely 
  crossed 
  

   near 
  its 
  upper 
  extremity 
  by 
  the 
  lateral 
  line. 
  The 
  clavicle 
  (PI. 
  I. 
  

   fig. 
  5, 
  cl.) 
  is 
  sharply 
  bent, 
  with 
  a 
  lower 
  limb 
  and 
  an 
  inner 
  laminar 
  

   expansion 
  as 
  in 
  Acipenser. 
  The 
  infra 
  clavicle 
  (i.cl.) 
  is 
  relatively 
  

   small 
  and 
  trapezoidal. 
  The 
  pectoral 
  fin-supports 
  are 
  unsatis- 
  

   factorily 
  known. 
  The 
  pelvic 
  fin-supports, 
  so 
  far 
  as 
  preserved, 
  are 
  a 
  

   single 
  regular 
  series 
  of 
  stout, 
  elongated 
  cartilages, 
  much 
  fewer 
  

   than 
  the 
  dermal 
  rays 
  ; 
  but 
  a 
  double 
  series 
  occurs 
  both 
  in 
  the 
  dorsal 
  

   and 
  anal, 
  the 
  baseosts 
  being 
  short, 
  and 
  the 
  axonosts 
  much 
  elongated, 
  

   extending 
  almost 
  or 
  quite 
  to 
  the 
  neural 
  and 
  haemal 
  spines 
  of 
  the 
  

   axial 
  skeleton. 
  

  

  The 
  large 
  fulcral 
  scales 
  at 
  the 
  base 
  of 
  the 
  upper 
  caudal 
  lobe 
  are 
  

   supported 
  by 
  a 
  distinct 
  series 
  of 
  vertically 
  elongated 
  cartilages 
  above 
  

   the 
  neural 
  arches. 
  

  

  Chondrosteus 
  acipenseroides, 
  Egerton. 
  

   [Plate 
  I. 
  figs. 
  1-5.] 
  

  

  1844. 
  Chondrosteus 
  accipenseroides, 
  L. 
  Agassiz, 
  Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  ii. 
  

  

  p. 
  280 
  (name 
  only). 
  

   1858. 
  Chondrosteus 
  acipenseroides, 
  Sir 
  P. 
  Egerton, 
  Phil. 
  Trans, 
  p. 
  871, 
  

  

  pis. 
  lxvii., 
  lxix., 
  pi. 
  lxviii. 
  fig. 
  2. 
  

   1858. 
  Chondrosteus 
  crassior, 
  Sir 
  P. 
  Egerton, 
  ibid. 
  p. 
  883, 
  pi. 
  lxviii. 
  

  

  fig. 
  1, 
  pi. 
  lxx. 
  [Head 
  ; 
  British 
  Museum.] 
  

   1887. 
  Chondrosteus 
  acipenseroides, 
  K. 
  H. 
  Traquair, 
  Geol. 
  Mag. 
  [3] 
  

  

  vol. 
  iv. 
  p. 
  248, 
  woodc. 
  figs. 
  1-5 
  (reprinted 
  in 
  Proc. 
  Roy. 
  Phys. 
  Soc. 
  

  

  Edinb. 
  vol. 
  ix. 
  p. 
  349, 
  with 
  woodcuts). 
  

   1887. 
  Chondrosteus 
  acipenseroides, 
  J. 
  W. 
  Davis, 
  Quart. 
  Journ. 
  Geol. 
  

  

  Soc. 
  vol. 
  xliii. 
  p. 
  605, 
  pi. 
  xxiii. 
  

   1889. 
  Chondrosteus 
  acip>enseroides, 
  A. 
  S. 
  Woodward, 
  Proc. 
  Geol. 
  Assoc. 
  

  

  vol. 
  xi. 
  p. 
  36, 
  woodc. 
  figs. 
  8-12. 
  

   1889. 
  Chondrosteus 
  acipenseroides, 
  M. 
  Browne, 
  Trans. 
  Leicester 
  Lit. 
  & 
  

  

  Phil. 
  Soc, 
  n. 
  s., 
  vol. 
  ii. 
  pt. 
  i. 
  p. 
  17, 
  pis. 
  i., 
  ii. 
  

  

  Type. 
  Imperfect 
  fish 
  ; 
  British 
  Museum. 
  

  

  The 
  type 
  species, 
  usually 
  attaining 
  a 
  length 
  not 
  exceeding 
  one 
  

   metre. 
  Maximum 
  depth 
  of 
  trunk 
  contained 
  about 
  five 
  and 
  a 
  half 
  

  

  