﻿254 
  

  

  THE 
  EXTINCT 
  VERTEBRATE 
  ANIMALS 
  

  

  description 
  of 
  an 
  entire 
  fish 
  is 
  extremely 
  rare. 
  One 
  nearly 
  entire 
  

   specimen, 
  though 
  wanting 
  the 
  pectoral 
  appendages, 
  is 
  figured 
  in 
  my 
  

   work 
  above 
  referred 
  to. 
  

  

  It 
  is 
  also 
  interesting 
  to 
  know 
  that 
  no 
  remains 
  of 
  Asterolepis 
  

   occur 
  in 
  any 
  other 
  bed 
  or 
  locality 
  in 
  Britain, 
  nor 
  is 
  the 
  genus 
  

   known 
  with 
  certainty 
  elsewhere 
  except 
  in 
  the 
  Upper 
  Devonian 
  of 
  

   Russia, 
  where 
  detached 
  plates 
  of 
  the 
  allied 
  A. 
  ornata 
  of 
  Eichwald 
  

   are 
  common 
  in 
  one 
  or 
  two 
  places, 
  especially 
  at 
  Wenden 
  in 
  

   Livonia. 
  

  

  Sub-class 
  TELEOSTOMI. 
  

   Order 
  CROSSOPTERYGII. 
  

   Family 
  HOLOPTYCHIIDiE. 
  

  

  Genus 
  HOLOPTYCHIUS, 
  Agassiz. 
  

   Holoptychius 
  decoratus 
  '(Eichwald), 
  1844. 
  

   Syn. 
  Sclerolepis 
  decwata, 
  Eichw. 
  

  

  (PI. 
  vi. 
  fig. 
  11, 
  scale, 
  natural 
  size.) 
  

   Scales, 
  one 
  to 
  two 
  inches 
  in 
  diameter, 
  rounded, 
  thin 
  ; 
  exposed 
  area 
  

   closely 
  covered 
  with 
  small 
  stellate 
  tubercles, 
  which 
  towards 
  the 
  

   covered 
  area 
  tend 
  to 
  become 
  abrupt 
  behind, 
  more 
  gently 
  sloping 
  

   in 
  front, 
  the 
  flattened 
  sloping 
  surface 
  being 
  marked 
  with 
  one 
  or 
  

   two 
  strong 
  sulci. 
  At 
  the 
  junction 
  of 
  the 
  exposed 
  and 
  covered 
  

   parts 
  of 
  the 
  scale 
  is 
  a 
  small 
  semilunar 
  area 
  of 
  minute 
  tubercles 
  

   closely 
  arranged 
  in 
  lines 
  radiating 
  forwards 
  and 
  outwards, 
  such 
  as 
  

   is 
  found 
  in 
  other 
  species 
  of 
  Holoptychius 
  and 
  Glyptolepis. 
  

  

  Other 
  Holoptychian 
  remains 
  attributable 
  to 
  this 
  species, 
  which 
  

   space 
  does 
  not 
  permit 
  me 
  to 
  figure, 
  are 
  : 
  — 
  

  

  A 
  mandible 
  of 
  a 
  short 
  and 
  deep 
  contour, 
  6 
  inches 
  in 
  length 
  and 
  

   If 
  inch 
  in 
  depth, 
  near 
  the 
  anterior 
  extremity. 
  There 
  are 
  no 
  

   teeth 
  preserved, 
  and 
  the 
  external 
  sculpture 
  is 
  lost 
  by 
  erosion. 
  

  

  A 
  mandibular 
  internal 
  dentary 
  bone 
  with 
  root 
  and 
  portion 
  of 
  

   shaft 
  of 
  a 
  laniary 
  tooth. 
  The 
  shaft 
  of 
  the 
  tooth 
  is 
  broken 
  off 
  

   shortly 
  above 
  the 
  base, 
  but 
  it 
  evidently 
  had 
  a 
  two-edged 
  contour 
  

   similar 
  to 
  that 
  of 
  the 
  laniaries 
  in 
  H. 
  giganteus, 
  Ag. 
  (=Lamnodus 
  

   bijporcalus, 
  Ag.). 
  

  

  A 
  clavicle, 
  inches 
  in 
  length, 
  showing 
  an 
  external 
  ornamen- 
  

   tation 
  of 
  minute 
  wavy 
  ridges. 
  

  

  