﻿CHONDROSTEID^E. 
  

  

  23 
  

  

  L. 
  G. 
  de 
  Koninck, 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xix. 
  (1863), 
  p. 
  17, 
  

   pi. 
  viii. 
  figs. 
  6, 
  7. 
  

  

  The 
  teeth 
  from 
  the 
  Muschelkalk 
  of 
  Jena 
  named 
  Thelodus 
  infleocus 
  

   by 
  E. 
  E. 
  Schmid 
  (he. 
  cit. 
  1861, 
  p. 
  27, 
  pi. 
  iv. 
  figs. 
  17-19) 
  are 
  also 
  

   very 
  doubtfully 
  placed 
  here. 
  Nothing 
  is 
  known 
  of 
  those 
  from 
  

   Laineck 
  recorded 
  as 
  SauriclitJiys 
  semistriatus, 
  Minister, 
  in 
  E. 
  Braun, 
  

   Yerzeichn. 
  Beyrouth 
  befindl. 
  Petrefact. 
  (1840), 
  p. 
  73. 
  

  

  A 
  fragmentary 
  fossil 
  from 
  the 
  Lower 
  Lias 
  of 
  Barrow-on-Soar 
  r 
  

   Leicestershire, 
  now 
  in 
  the 
  Leicester 
  Museum, 
  has 
  been 
  provisionally 
  

   associated 
  with 
  Belonorhynchus 
  and 
  Sau?*ichthys, 
  under 
  the 
  name 
  of 
  

   Browneichtliys 
  ornatus 
  (A. 
  S. 
  Woodward, 
  Geol. 
  Mag. 
  [3] 
  vol. 
  vi. 
  

   1889, 
  p. 
  455). 
  The 
  bones 
  of 
  the 
  head 
  are 
  invested 
  with 
  ganoine 
  

   and 
  ornamented 
  with 
  large 
  tuberculations. 
  The 
  notochord 
  seems 
  

   to 
  have 
  been 
  persistent. 
  At 
  least 
  the 
  front 
  portion 
  of 
  the 
  trunk 
  is 
  

   covered 
  with 
  thin, 
  deeply 
  overlapping 
  scales, 
  oval 
  or 
  round 
  in 
  shape, 
  

   with 
  prominent 
  concentric 
  lines 
  of 
  growth, 
  and 
  externally 
  orna- 
  

   mented 
  with 
  large 
  ganoine 
  tubercles. 
  There 
  was 
  also 
  a 
  partial 
  or 
  

   continuous 
  armature 
  of 
  the 
  dorsal 
  and 
  ventral 
  margins, 
  consisting 
  

   of 
  large, 
  narrow, 
  pointed 
  ridge-scales. 
  

  

  Family 
  CHONDEOSTEID.E. 
  

  

  Trunk 
  elongate-fusiform 
  ; 
  tail 
  heterocercal. 
  Head-bones 
  well- 
  

   developed, 
  those 
  of 
  the 
  cranial 
  roof 
  forming 
  a 
  continuous 
  shield, 
  

   without 
  a 
  median 
  longitudinal 
  series 
  of 
  azygous 
  elements 
  ; 
  snout 
  

   prominent 
  and 
  eye 
  far 
  forwards 
  ; 
  no 
  premaxilla 
  ; 
  dentition 
  rudi- 
  

   mentary 
  or 
  absent; 
  operculum 
  and 
  suboperculum 
  present, 
  with 
  a 
  

   few 
  well-developed 
  branchiostegal 
  rays. 
  Squamation 
  rudimentary 
  

   or 
  absent 
  on 
  the 
  trunk, 
  robust 
  on 
  the 
  upper 
  caudal 
  lobe. 
  

  

  Only 
  one 
  definable 
  genus 
  of 
  this 
  family, 
  Chondrosteus, 
  has 
  hitherto 
  

   been 
  discovered; 
  but 
  it 
  seems 
  probable 
  that 
  the 
  fragmentarily- 
  

   known 
  genus 
  Gyrosteus 
  will 
  prove 
  to 
  be 
  correctly 
  placed 
  here. 
  

  

  Genus 
  CHONDROSTEUS, 
  Egerton. 
  

   [Phil. 
  Trans. 
  1858, 
  p. 
  871 
  (ex 
  Agassiz, 
  MS.).] 
  

  

  External 
  bones 
  feebly 
  ornamented 
  with 
  granulations, 
  partly 
  

   coated 
  with 
  ganoine 
  ; 
  mandibular 
  suspensorium 
  very 
  oblique 
  ; 
  jaws 
  

   toothless 
  ; 
  maxilla 
  arched, 
  much 
  expanded 
  behind 
  and 
  tapering 
  in 
  

   front, 
  without 
  process 
  for 
  palatine 
  articulation 
  ; 
  suboperculum 
  

   large 
  and 
  quadrate, 
  operculum 
  relatively 
  small 
  and 
  triangular. 
  

   Eibs 
  absent. 
  Ein-rays 
  covered 
  with 
  a 
  very 
  thin 
  film 
  of 
  ganoine, 
  

   the 
  pectorals 
  also 
  sparsely 
  granulated 
  ; 
  all 
  closely 
  articulated 
  except 
  

   a 
  few 
  anterior 
  pectorals, 
  which 
  are 
  not 
  enlarged 
  ; 
  fulcra 
  absent, 
  

  

  