﻿VERTEBRATES. 
  247 
  

  

  posteriorly, 
  and 
  are 
  quite 
  uniformly 
  marked 
  by 
  slightly 
  oblique 
  

   transverse 
  ridges 
  slightly 
  raised 
  and 
  culminating 
  above 
  in 
  a 
  low 
  

   crest, 
  the 
  unworn 
  slopes 
  and 
  depressions 
  being 
  beautifully 
  sculp- 
  

   tured 
  logitudinally 
  by 
  delicate 
  thread-like 
  lines 
  crossed 
  by 
  extremely 
  

   fine 
  transverse 
  or 
  oblique 
  rugae, 
  the 
  lateral 
  edges 
  similarly 
  orna- 
  

   mented 
  as 
  noticed 
  in 
  the 
  dorsal 
  ridge 
  ; 
  the 
  nodose 
  character 
  of 
  the 
  

   transverse 
  ridges 
  increases 
  toward 
  the 
  postero-lateral 
  angles, 
  how- 
  

   ever, 
  retaining 
  the 
  details 
  described, 
  and 
  in 
  worn 
  specimens 
  the 
  

   lateral 
  costae 
  show 
  more 
  or 
  less 
  smooth 
  crests, 
  the 
  extremities 
  of 
  

   the 
  tubercles 
  producing 
  the 
  pectinated 
  or 
  crenulated 
  lateral 
  borders 
  

   observed 
  in 
  abraded 
  specimens, 
  like 
  the 
  original 
  or 
  type 
  exam- 
  

   ple 
  of 
  the 
  species 
  ; 
  the 
  costae 
  increase 
  by 
  bifurcation 
  and 
  implan- 
  

   tation 
  below 
  at 
  frequent 
  intervals. 
  The 
  intercostal 
  sulci 
  are 
  perhaps 
  

   one-half 
  the 
  diameter 
  of 
  the 
  ribs, 
  presenting 
  a 
  furrow 
  of 
  moderate 
  

   depth, 
  striato-punctate, 
  that 
  on 
  either 
  side 
  of 
  the 
  dorsal 
  ridge 
  and 
  

   others 
  showing 
  occasional 
  irregularly 
  dispersed 
  tubercles 
  orna- 
  

   mented 
  precisely 
  after 
  the 
  style 
  observed 
  in 
  the 
  costal 
  tubercula- 
  

   tions. 
  Postero-lateral 
  angles 
  sharply 
  defined, 
  skirted 
  by 
  a 
  narrow, 
  

   faintly 
  depressed 
  outer 
  belt 
  of 
  the 
  posterior 
  face, 
  which 
  rises 
  into 
  a 
  

   low 
  angular 
  ridge 
  defining 
  the 
  regularly 
  transversely 
  concave, 
  mod- 
  

   erately 
  deep 
  median 
  furrow 
  occupying 
  more 
  than 
  half 
  the 
  lateral 
  

   area, 
  and 
  which 
  is 
  coarsely 
  pitted 
  or 
  striato-punctate 
  ; 
  immediately 
  

   along 
  the 
  outer 
  side 
  of 
  the 
  lateral 
  crests 
  occur 
  a 
  row 
  of 
  depressed, 
  

   obovate, 
  closely 
  arranged 
  tubercles, 
  spaced 
  by 
  less 
  than 
  half 
  their 
  

   longer 
  or 
  longitudinal 
  diameter, 
  constricted 
  basally 
  and 
  culmin- 
  

   ating 
  in 
  a 
  low 
  crest 
  overhanging 
  the 
  upper 
  border, 
  similarly 
  marked 
  

   by 
  delicate 
  thread-like 
  lines 
  already 
  remarked. 
  The 
  pulp 
  cavity 
  is 
  

   of' 
  moderate 
  capacity, 
  compressed-oval 
  in 
  transverse 
  section, 
  and 
  in 
  

   an 
  example 
  of 
  at 
  least 
  150 
  millimetres 
  in 
  length 
  it 
  extends 
  to 
  

   within 
  20 
  mm. 
  of 
  the 
  distal 
  extremity, 
  apparently 
  opening 
  out 
  in 
  

   the 
  posterior 
  face 
  little 
  if 
  any 
  above 
  the 
  dorsal 
  line, 
  which 
  latter 
  

   has 
  a 
  rather 
  oblique 
  upward 
  course 
  from 
  the 
  anterior 
  dorsal 
  angle, 
  

   inserted 
  base 
  longitudinally 
  striato-punaiate, 
  proportionately 
  of 
  con- 
  

   siderable 
  depth, 
  perhaps 
  equal 
  to 
  a 
  fourth 
  of 
  the 
  entire 
  length 
  of 
  

   the 
  spine. 
  

  

  The 
  above 
  description 
  is 
  founded 
  upon 
  two 
  specimens 
  : 
  one, 
  the 
  

   original 
  examined 
  by 
  Messrs. 
  Newberry 
  and 
  Worthen, 
  representing 
  

   a 
  small-size 
  spine 
  about 
  60 
  millimetres 
  in 
  length, 
  showing 
  one 
  side 
  

   with 
  patches 
  of 
  the 
  worn 
  costae 
  and 
  dorsal 
  ridge 
  which 
  apparently 
  

   terminate 
  at 
  the 
  oblique 
  dorsal 
  line; 
  the 
  posterior 
  face 
  is 
  broken 
  

   away. 
  The 
  other 
  specimen 
  preserves 
  nearly 
  111 
  millimetres 
  of 
  a 
  

  

  