﻿34 
  ACTINOPTERYGHI. 
  

  

  P. 
  7398. 
  Plaster 
  cast 
  of 
  tail, 
  the 
  original 
  being 
  the 
  type 
  specimen 
  

   described 
  by 
  Egerton, 
  loc. 
  cit. 
  ; 
  Lyme 
  Eegis. 
  This 
  is 
  

   supposed 
  to 
  belong 
  to 
  the 
  same 
  individual 
  as 
  one 
  of 
  the 
  

   following 
  specimens. 
  

  

  28714. 
  Crushed 
  remains 
  of 
  head 
  and 
  pectoral 
  arch, 
  with 
  a 
  few 
  

   fragmentary 
  neural 
  arches 
  of 
  the 
  trunk 
  and 
  some 
  well- 
  

   preserved 
  pectoral 
  fin-rays, 
  noticed 
  by 
  Egerton, 
  loc. 
  cit., 
  

   and 
  by 
  the 
  present 
  writer 
  in 
  Proc. 
  Geoi. 
  Assoc, 
  vol. 
  xi. 
  

   (1889), 
  p. 
  36 
  ; 
  Lyme 
  Eegis. 
  The 
  tuberculations 
  on 
  the 
  

   pectoral 
  fin-rays 
  are 
  shown. 
  Purchased, 
  1853. 
  

  

  28714 
  a. 
  Slab 
  exhibiting 
  the 
  external 
  tuberculated 
  surface 
  of 
  three 
  

   of 
  the 
  cranial 
  roof-bones 
  and 
  other 
  fragments, 
  with 
  an 
  

   imperfect 
  clavicle, 
  described 
  by 
  Egerton, 
  loc. 
  cit. 
  ; 
  Lyme 
  

   Eegis. 
  The 
  two 
  principal 
  cranial 
  bones 
  are 
  described 
  as 
  

   mastoids 
  (i. 
  e., 
  squamosals), 
  and 
  the 
  clavicle 
  appears 
  to 
  be 
  

   referred 
  to 
  as 
  " 
  suprascapular 
  Purchased, 
  1853. 
  

  

  Genus 
  GYROSTEUS, 
  A. 
  S. 
  Woodward. 
  

  

  [Proc. 
  Geol. 
  Assoc, 
  vol. 
  xi. 
  1889, 
  p. 
  36 
  (ex 
  Agassiz, 
  MS.).] 
  

  

  An 
  imperfectly 
  definable 
  genus 
  comprising 
  fishes 
  of 
  large 
  size, 
  

   hitherto 
  known 
  only 
  by 
  fragmentary 
  specimens. 
  External 
  bones 
  

   with 
  or 
  without 
  a 
  feeble 
  ornamentation, 
  destitute 
  of 
  ganoine 
  ; 
  jaws 
  

   toothless 
  ; 
  maxilla 
  arched, 
  not 
  much 
  expanded 
  behind, 
  but 
  with 
  a 
  

   great 
  upward 
  and 
  inward 
  extension 
  in 
  its 
  anterior 
  half 
  for 
  palatine- 
  

   pterygoid 
  articulation 
  ; 
  hyomandibular 
  completely 
  ossified 
  ; 
  sub- 
  

   operculum 
  (?) 
  large 
  and 
  quadrate. 
  Small 
  ossified 
  ribs 
  present 
  (?). 
  

   Scales 
  absent, 
  except 
  on 
  the 
  upper 
  caudal 
  lobe, 
  where 
  they 
  are 
  

   thick 
  ; 
  caudal 
  fulcral 
  scales 
  large, 
  without 
  ganoine. 
  

  

  Gyrosteus 
  mirabilis, 
  Agassiz, 
  MS. 
  

  

  1844. 
  Gyrosteus 
  mirabilis, 
  L. 
  Agassiz, 
  Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  ii. 
  p. 
  179 
  

  

  (name 
  only). 
  

   1855. 
  Sepia 
  incomposita, 
  M. 
  Simpson, 
  Foss. 
  Yorkshire 
  Lias, 
  p. 
  21. 
  

  

  [Fragment 
  of 
  bone 
  ; 
  Whitby 
  Museum.] 
  

   1858. 
  Gyrosteus 
  mirabilis, 
  Sir 
  P. 
  Egerton, 
  Phil. 
  Trans, 
  p. 
  883. 
  

   1876. 
  Gyrosteus 
  mirabilis, 
  J. 
  F. 
  Blake, 
  in 
  Tate 
  & 
  Blake, 
  Yorkshire 
  

  

  Lias, 
  p. 
  256, 
  pi. 
  ii. 
  figs. 
  2, 
  3. 
  

   1889-90. 
  Gyrosteus 
  mirabilis, 
  A. 
  S. 
  Woodward, 
  Proc. 
  Geol. 
  Assoc. 
  

  

  vol. 
  xi. 
  p. 
  32, 
  figs. 
  2-7; 
  and 
  The 
  Naturalist, 
  1890, 
  p. 
  101, 
  

  

  figs. 
  1-6. 
  

  

  