﻿1864.] 
  LANKESTER 
  SCALES 
  OF 
  PTERASPIS. 
  195 
  

  

  the 
  Cornstones 
  of 
  Herefordshire, 
  associated 
  with 
  the 
  well-known 
  

   Cephalaspis 
  Lyellii. 
  He 
  considered 
  these 
  remains 
  as 
  portions 
  of 
  

   the 
  cephalic 
  shield 
  of 
  three 
  distinct 
  species 
  of 
  Cephalaspis, 
  which 
  

   he 
  named 
  C. 
  rostmtus, 
  C. 
  Lewisii, 
  and 
  C. 
  Lloydii, 
  respectively. 
  

   At 
  the 
  same 
  time 
  he 
  expressed 
  his 
  doubts 
  as 
  to 
  whether, 
  on 
  account 
  

   of 
  the 
  peculiar 
  structure 
  of 
  the 
  test, 
  it 
  might 
  not 
  be 
  advisable 
  to 
  

   place 
  these 
  three 
  Fish 
  in 
  a 
  distinct 
  genus. 
  In 
  1847, 
  Dr. 
  It. 
  Kner, 
  

   writing 
  in 
  Haidinger's 
  * 
  Abhandlungen 
  *,' 
  considered 
  the 
  fossils 
  in 
  

   question 
  as 
  the 
  remains 
  of 
  Cephalopoda, 
  and 
  he 
  proposed, 
  therefore, 
  

   to 
  place 
  them 
  in 
  a 
  new 
  genus, 
  Pteraspis, 
  remarking 
  that 
  the 
  struc- 
  

   ture 
  of 
  the 
  test 
  preserved 
  in 
  these 
  fossils 
  corresponded 
  closely 
  with 
  

   that 
  of 
  the 
  calcareous 
  plate 
  or 
  " 
  cuttle-bone 
  " 
  of 
  Sepia. 
  Prof. 
  

   Huxley 
  has 
  since 
  investigated 
  the 
  structure 
  of 
  both 
  Cephalaspis 
  

   and 
  Pteraspis, 
  and 
  published 
  his 
  results 
  in 
  this 
  Journal 
  f 
  . 
  It 
  will 
  

   therefore 
  only 
  be 
  necessary 
  to 
  remark 
  that 
  he 
  came 
  to 
  the 
  con- 
  

   clusion 
  that 
  Pteraspis 
  Lewisii, 
  P. 
  Lloydii, 
  and 
  P. 
  rostratus 
  were 
  

   the 
  remains 
  of 
  Fish, 
  and 
  presented 
  no 
  real 
  analogy 
  to 
  Sepia 
  in 
  the 
  

   microscopic 
  structure 
  of 
  the 
  test. 
  This, 
  he 
  showed, 
  was 
  similar 
  to 
  

   that 
  of 
  Cephalaspis, 
  but 
  differed 
  in 
  the 
  absence 
  of 
  bone-cells 
  or 
  

   lacunae 
  ; 
  and 
  he 
  adopted 
  Kner's 
  name 
  of 
  Pteraspis 
  for 
  these 
  Fish, 
  

   considering 
  that 
  the 
  differences 
  in 
  form 
  and 
  structure 
  between 
  the 
  

   two 
  groups 
  warranted 
  a 
  generic 
  separation. 
  

  

  The 
  only 
  thing 
  required 
  to 
  remove 
  the 
  doubts 
  which 
  yet 
  lingered 
  

   in 
  the 
  minds 
  of 
  some 
  palaeontologists 
  as 
  to 
  the 
  piscine 
  nature 
  of 
  

   Pteraspis 
  was 
  the 
  discovery 
  of 
  the 
  scales. 
  These, 
  at 
  length, 
  have 
  

   come 
  to 
  light, 
  in 
  a 
  quarry 
  at 
  Cradley, 
  near 
  Malvern, 
  where 
  the 
  

   Cornstones 
  of 
  the 
  Devonian 
  system 
  are 
  worked. 
  The 
  specimen 
  

   (PI. 
  XII. 
  figs. 
  3 
  & 
  4) 
  which 
  I 
  obtained 
  last 
  summer 
  consists 
  of 
  a 
  small 
  

   portion 
  of 
  the 
  cephalic 
  shield, 
  of 
  which 
  the 
  internal 
  nacreous 
  layer 
  

   is 
  exposed 
  ; 
  closely 
  attached 
  to 
  its 
  posterior 
  margin, 
  and 
  apparently 
  

   partially 
  underlying 
  it, 
  is 
  a 
  row 
  of 
  rhomboidal 
  scales, 
  eight 
  in 
  

   number 
  ; 
  these 
  are 
  followed 
  by 
  eight 
  other 
  rows 
  of 
  similar 
  scales, 
  

   and 
  they 
  are 
  all 
  that 
  remained 
  preserved 
  in 
  the 
  specimen. 
  The 
  

   scales 
  which 
  are 
  shown 
  are, 
  therefore, 
  only 
  those 
  of 
  a 
  small 
  portion 
  

   of 
  the 
  anterior 
  dorsal 
  surface. 
  

  

  It 
  might 
  be 
  suggested 
  that 
  these 
  were 
  the 
  scales 
  of 
  some 
  other 
  

   Fish, 
  since 
  the 
  portion 
  of 
  the 
  cephalic 
  shield 
  preserved 
  is 
  hardly 
  

   sufficient 
  from 
  its 
  form 
  alone 
  to 
  warrant 
  the 
  assumption 
  of 
  their 
  

   Pteraspidian 
  nature. 
  Fortunately, 
  however, 
  on 
  one 
  surface 
  of 
  the 
  

   specimen 
  (which 
  presents 
  a 
  part 
  of 
  the 
  shield 
  crushed 
  into 
  this 
  

   position) 
  a 
  small 
  portion 
  of 
  the 
  characteristic 
  external 
  layer 
  of 
  the 
  

   testis 
  shown. 
  This 
  is 
  marked 
  superficially 
  by 
  delicate 
  striae 
  running 
  

   parallel 
  to 
  one 
  another 
  ; 
  and 
  at 
  the 
  edge, 
  where 
  broken 
  off, 
  it 
  shows 
  

   the 
  middle 
  layer 
  containing 
  the 
  polygonal 
  cavities 
  described 
  by 
  Prof. 
  

   Huxley. 
  This 
  structure, 
  which 
  has 
  no 
  parallel 
  among 
  Fishes, 
  or, 
  

   indeed, 
  any 
  group 
  of 
  the 
  animal 
  kingdom, 
  leaves 
  no 
  possibility 
  of 
  a 
  

   doubt 
  that 
  the 
  specimen 
  is 
  a 
  fragment 
  of 
  Pteraspis. 
  

  

  * 
  Haidinger's 
  ' 
  Naturwissenschaftliche 
  Abhandlungen,' 
  vol. 
  i. 
  p. 
  159. 
  

   t 
  Quart. 
  Journ. 
  Greol. 
  Soc. 
  vol. 
  xiv. 
  p. 
  267. 
  

  

  