﻿VEKTEBKATES. 
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  nouneed 
  and 
  quite 
  persistent 
  in 
  their 
  uniformity. 
  Median 
  ridge 
  

   rising 
  into 
  a 
  rather 
  sharply 
  rounded 
  crest 
  nearly 
  median 
  in 
  posi- 
  

   tion, 
  the 
  anterior 
  slope 
  moderate 
  and 
  slightly 
  concave 
  transversely, 
  

   terminating 
  in 
  a 
  shallow 
  depression 
  bordered 
  by 
  a 
  very 
  narrow 
  fold 
  

   immediately 
  along 
  the 
  antero-lateral 
  border; 
  posteriorly 
  the 
  surface 
  

   abruptly 
  descends 
  into 
  the 
  depression 
  on 
  that 
  side, 
  whence 
  the 
  

   alate 
  expansion 
  gradually 
  rises 
  with 
  slight 
  transverse 
  concavity 
  into 
  

   the 
  moderately 
  elevated 
  postero-lateral 
  border. 
  The 
  coronal 
  surface 
  

   is 
  quite 
  regularly 
  marked 
  by 
  transverse 
  rugae 
  parallel 
  with 
  the 
  

   inner 
  margin, 
  the 
  interspaces 
  nearly 
  a 
  millimetre 
  in 
  breadth 
  and 
  

   rising 
  from 
  below 
  upward 
  producing 
  a 
  reversed 
  imbricated 
  appear- 
  

   ance. 
  The 
  ornamental 
  rugae 
  are 
  most 
  distinct 
  over 
  the 
  depressed 
  

   areas; 
  in 
  the 
  more 
  elevated 
  exposed 
  portions 
  of 
  the 
  surface 
  they 
  

   are 
  usually 
  obsolete; 
  however, 
  there 
  are 
  traces 
  of 
  their 
  presence 
  

   over 
  the 
  entire 
  area 
  of 
  the 
  coronal 
  region. 
  The 
  punctate 
  structure 
  

   presents 
  the 
  usual 
  appearances 
  associated 
  with 
  teeth 
  whose 
  coronal 
  

   surface 
  is 
  traversed 
  by 
  transverse 
  ridges 
  and 
  furrows, 
  the 
  punctae 
  

   being 
  elongated 
  usually 
  in 
  the 
  direction 
  of 
  inrollment 
  along 
  the 
  

   transverse 
  folds 
  ; 
  exfoliated 
  and 
  worn 
  surfaces 
  showing 
  a 
  relatively 
  

   minute, 
  crowded 
  punctation. 
  Transverse 
  diameter 
  at 
  the 
  inner 
  

   margin 
  of 
  a 
  medium-size 
  tooth 
  20 
  mm. 
  ; 
  length 
  of 
  antero-lateral 
  

   border 
  to 
  point 
  of 
  inrollment 
  10.5 
  mm. 
  

  

  Mandibular 
  median 
  tooth 
  of 
  proportionate 
  size 
  in 
  relation 
  to 
  the 
  

   posterior 
  form, 
  trapezoidal 
  in 
  outline, 
  elongated 
  in 
  the 
  direction 
  of 
  

   inrollment. 
  Postero-lateral 
  border 
  nearly 
  straight, 
  opposite 
  border 
  

   converging 
  toward 
  the 
  outer 
  extremity 
  at 
  an 
  angle 
  of 
  about 
  20°, 
  

   inner 
  margin 
  very 
  oblique 
  with 
  a 
  slight 
  sigmoidal 
  curvature 
  from 
  

   the 
  sharply 
  rounded 
  posterior 
  angle 
  to 
  the 
  obtuse 
  anterior 
  angle. 
  

   Coronal 
  ridge 
  situated 
  posterior 
  of 
  the 
  median 
  line, 
  of 
  moderate 
  

   prominence 
  and 
  breadth, 
  posterior 
  slope 
  abrupt 
  and 
  deep 
  to 
  the 
  

   narrow 
  furrow 
  close 
  along 
  the 
  postero-lateral 
  border, 
  over 
  which 
  the 
  

   coronal 
  enamel 
  forms 
  a 
  narrow 
  inbeveled 
  fold 
  ; 
  anterior 
  declivity 
  

   nearly 
  equally 
  steep 
  but 
  of 
  less 
  depth, 
  defined 
  by 
  a 
  rounded 
  angu- 
  

   lation 
  whence 
  the 
  surface 
  more 
  gently 
  descends 
  with 
  slight 
  trans- 
  

   verse 
  convexity 
  to 
  the 
  antero-lateral 
  border 
  just 
  within 
  which 
  lies 
  a 
  

   shallow 
  parallel 
  furrow 
  recalling 
  that 
  adjacent 
  the 
  articular 
  border 
  

   of 
  the 
  terminal 
  tooth. 
  Along 
  the 
  posterior 
  border 
  and 
  over 
  a 
  large 
  

   part 
  of 
  the 
  anterior 
  slope 
  the 
  surface 
  preserves 
  the 
  parallel, 
  rarely 
  

   bifurcating 
  transverse 
  rugae, 
  conforming 
  to 
  the 
  direction 
  of 
  the 
  inner 
  

   margin, 
  and 
  spaced 
  as 
  previously 
  noted 
  in 
  relation 
  to 
  the 
  last 
  

   described 
  form, 
  with 
  which 
  the 
  general 
  character 
  of 
  the 
  surface 
  

  

  