﻿264 
  

  

  THE 
  EXTINCT 
  VERTEBRATE 
  ANIMALS 
  

  

  sidered 
  by 
  him 
  to 
  be 
  a 
  selachian 
  spine, 
  was 
  interpreted 
  by 
  

   Pander 
  as 
  the 
  penultimate 
  plate 
  (external 
  marginal) 
  of 
  an 
  Astero- 
  

   lepid 
  ' 
  forearm.' 
  On 
  the 
  acquisition, 
  by 
  the 
  Edinburgh 
  Museum, 
  

   in 
  1892, 
  of 
  the 
  Powrie 
  Collection, 
  in 
  which 
  the 
  original 
  specimen 
  

   was 
  contained, 
  I 
  expressed 
  the 
  opinion 
  (48, 
  p. 
  36) 
  that 
  the 
  

   sculpture 
  of 
  Cosmacanthus 
  Malcolmsoni 
  was 
  ' 
  different 
  from 
  that 
  on 
  

   the 
  arms 
  of 
  Bothriolepis 
  majoi\ 
  the 
  common 
  Asterolepid 
  of 
  the 
  

   Scaat 
  Craig 
  deposit,' 
  though 
  at 
  the 
  same 
  time 
  I 
  did 
  not 
  consider 
  

   it 
  to 
  be 
  a 
  selachian 
  spine. 
  Previously, 
  however, 
  M'Coy 
  and 
  

   Davis 
  had 
  referred 
  no 
  less 
  than 
  four 
  species 
  of 
  selachian 
  spines 
  

   from 
  the 
  carboniferous 
  limestone 
  of 
  Armagh 
  to 
  the 
  genus. 
  1 
  

  

  To 
  the 
  kindness 
  of 
  Mr. 
  W. 
  Taylor 
  I 
  owe 
  a 
  large 
  fragment 
  of 
  

   the 
  same 
  body, 
  which 
  was 
  found 
  by 
  him 
  at 
  the 
  same 
  locality 
  

   in 
  the 
  course 
  of 
  the 
  summer 
  of 
  the 
  present 
  year 
  (1895), 
  and 
  

   which 
  I 
  have 
  represented 
  in 
  PI. 
  vi. 
  figs. 
  6-9. 
  It 
  is 
  a 
  portion 
  

   of 
  the 
  basal 
  extremity 
  of 
  a 
  spine, 
  1^ 
  inch 
  in 
  length, 
  by 
  nearly 
  

   half 
  an 
  inch 
  in 
  breadth, 
  laterally 
  compressed, 
  and 
  showing 
  two 
  

   margins, 
  besides 
  the 
  extremities, 
  both 
  of 
  which 
  are 
  broken 
  off. 
  

   One 
  margin, 
  gently 
  curved 
  and 
  very 
  narrow, 
  shows 
  two 
  rows 
  of 
  

   small 
  tubercles, 
  as 
  in 
  the 
  type 
  specimen 
  ; 
  the 
  opposite 
  margin, 
  or 
  

   rather 
  aspect, 
  shows 
  a 
  wide 
  cleft 
  opening 
  into 
  the 
  internal 
  cavity 
  

   of 
  the 
  spine, 
  and 
  which 
  closes 
  up 
  just 
  before 
  the 
  specimen 
  is 
  

   broken 
  off 
  distally, 
  and 
  there 
  it 
  becomes 
  a 
  slight 
  groove, 
  which 
  is 
  

   not, 
  however, 
  quite 
  symmetrically 
  placed, 
  as 
  it 
  looks 
  more 
  to 
  one 
  

   (the 
  more 
  convex) 
  side 
  than 
  to 
  the 
  other. 
  Nor 
  are 
  the 
  two 
  sides 
  

   symmetrical, 
  for 
  one 
  is 
  slightly 
  more 
  convex 
  than 
  the 
  other, 
  which 
  

   is 
  nearly 
  flat 
  ; 
  both 
  are 
  covered 
  with 
  small, 
  irregularly-placed 
  

   stellate-based 
  tubercles, 
  which 
  are 
  somewhat 
  larger 
  on 
  the 
  more 
  

   convex 
  of 
  the 
  two 
  sides 
  ; 
  there 
  is, 
  however, 
  a 
  longitudinal 
  narrow 
  

   groove, 
  free 
  of 
  tubercles, 
  running 
  along 
  the 
  edge 
  of 
  each 
  of 
  the 
  

   sides, 
  where 
  it 
  forms 
  the 
  lip 
  of 
  the 
  open 
  part 
  of 
  the 
  internal 
  

   cavity. 
  The 
  broken 
  distal 
  aspect 
  of 
  the 
  spine 
  shows 
  a 
  shut-off 
  

   continuation 
  of 
  this 
  cavity, 
  which 
  is 
  very 
  narrowly 
  oval 
  in 
  trans- 
  

   verse 
  action. 
  The 
  fractural 
  surfaces 
  show 
  that 
  the 
  interior 
  of 
  the 
  

   tissue 
  is 
  permeated 
  by 
  a 
  very 
  close 
  network 
  of 
  vascular 
  canals, 
  

   though 
  I 
  have 
  not 
  ventured 
  to 
  make 
  so 
  fragmentary 
  a 
  specimen 
  

   smaller 
  still 
  by 
  taking 
  off 
  a 
  piece 
  for 
  microscopic 
  investigation. 
  

  

  1 
  See 
  J. 
  W. 
  Davis, 
  in 
  1 
  Fossil 
  Fishes 
  of 
  the 
  Carboniferous 
  Limestone 
  Series,' 
  

   Sc. 
  Trans. 
  Roy. 
  Dublin 
  Society, 
  vol. 
  i. 
  ser. 
  2, 
  1883, 
  pp. 
  355-358. 
  

  

  