﻿VEKTEBBATES. 
  157 
  

  

  and 
  on 
  the 
  other 
  merging 
  into 
  the 
  posterior 
  depression, 
  whose 
  pos- 
  

   terolateral 
  border 
  is 
  broken 
  away, 
  as 
  also 
  the 
  inner 
  and 
  outer 
  por- 
  

   tions 
  of 
  the 
  tooth. 
  The 
  form 
  was 
  evidently 
  sub-cuneate 
  in 
  outline. 
  

   The 
  coronal 
  surface 
  exhibits 
  the 
  same 
  punctate 
  characters 
  noticed 
  

   in 
  connection 
  with 
  the 
  terminal 
  form 
  ; 
  however, 
  the 
  transverse 
  undu- 
  

   lations 
  are 
  less 
  conspicuous. 
  The 
  relative 
  size 
  agrees 
  with 
  the 
  pre- 
  

   ceding 
  form 
  with 
  which 
  it 
  was 
  associated. 
  

  

  Posterior 
  tooth 
  of 
  the 
  upper 
  jaw 
  elongate 
  triangular 
  in 
  outline, 
  

   rather 
  strongly 
  arched 
  from 
  within 
  outward, 
  and 
  spirally 
  inrolled. 
  

   Anterior 
  articular 
  border 
  comprising, 
  perhaps, 
  two-thirds 
  of 
  the 
  great- 
  

   est 
  length 
  of 
  the 
  tooth 
  from 
  the 
  inrolled 
  outer 
  margin 
  to 
  the 
  very 
  

   produced 
  inner 
  angle 
  at 
  the 
  base 
  of 
  the 
  principal 
  coronal 
  ridge, 
  

   gently 
  curved 
  sigmoidally, 
  the 
  narrow 
  enamel 
  fold 
  strongly 
  inbeveled 
  

   to 
  the 
  deeply-channeled, 
  shallow 
  basal 
  rim; 
  postero-lateral 
  border 
  

   converging 
  at 
  an 
  angle 
  of 
  45°, 
  more 
  or 
  less, 
  with 
  the 
  anterior 
  artic- 
  

   ular 
  border* 
  gently 
  curved, 
  the 
  thick 
  enamel 
  fold 
  rounded 
  and 
  

   sharply 
  inbeveled 
  to 
  the 
  correspondingly 
  deep, 
  flaring 
  basal 
  border, 
  

   from 
  which 
  it 
  is 
  defined 
  by 
  a 
  deep 
  sulcus 
  ; 
  inner 
  margin 
  making 
  a 
  

   slight 
  angle 
  with 
  the 
  articular 
  border 
  in 
  front, 
  suddenly 
  deflected 
  

   nearly 
  at 
  right 
  angles 
  in 
  rounding 
  the 
  base 
  of 
  the 
  coronal 
  ridge, 
  and 
  

   thence 
  passing 
  to 
  the 
  posterior 
  angle 
  with 
  a 
  slight 
  concavity 
  in 
  the 
  

   region 
  of 
  the 
  posterior 
  depression, 
  worn 
  specimens 
  inbeveled 
  interi- 
  

   orly. 
  Principal 
  coronal 
  ridge 
  culminating 
  in 
  a 
  rather 
  sharply 
  rounded 
  

   crest 
  about 
  one-fourth 
  the 
  distance 
  from 
  the 
  anterior 
  border, 
  pre- 
  

   senting' 
  a 
  steep 
  convexity 
  descending 
  to 
  the 
  shallow 
  depressed 
  belt 
  

   bordering 
  the 
  articular 
  fold, 
  on 
  the 
  opposite 
  side 
  gently 
  descending 
  

   into 
  the 
  wide 
  posterior 
  depression 
  from 
  which 
  abruptly 
  rises 
  the 
  

   narrow, 
  transversely 
  arched 
  alate 
  expansion, 
  and 
  from 
  which 
  it 
  is 
  

   defined 
  by 
  a 
  distinct 
  augulation. 
  The 
  coronal 
  surface 
  is 
  more 
  or 
  

   less 
  regularly 
  undulated 
  transversely, 
  producing 
  a 
  nodose 
  appearance 
  

   along 
  the 
  crest 
  of 
  the 
  principal 
  ridge. 
  The 
  character 
  of 
  the 
  deli- 
  

   cately 
  rugose 
  enamel 
  enveloping 
  the 
  inner 
  portion 
  of 
  the 
  crown, 
  and 
  

   the 
  punctation 
  of 
  the 
  outer 
  worn 
  surface, 
  is 
  precisely 
  as 
  observed 
  in 
  

   the 
  opposed 
  teeth 
  of 
  the 
  mandible. 
  In 
  both 
  forms, 
  also, 
  the 
  smooth 
  

   or 
  faintly 
  longitudinally 
  striated 
  inferior 
  surface 
  approximately 
  con- 
  

   forms 
  to 
  the 
  contour 
  of 
  the 
  coronal 
  region, 
  showing 
  the 
  usual 
  dense 
  

   thin 
  basal 
  layer. 
  Length 
  of 
  a 
  large 
  tooth 
  along 
  the 
  anterior 
  articu- 
  

   lar 
  border 
  to 
  inrolled 
  outer 
  margin, 
  32 
  mm. 
  or 
  more 
  ; 
  greatest 
  length 
  

   of 
  tooth 
  along 
  the 
  crest 
  of 
  the 
  coronal 
  ridge, 
  58 
  mm. 
  ; 
  breadth 
  be- 
  

   tween 
  inner 
  angles 
  of 
  the 
  tooth, 
  about 
  51 
  mm. 
  ; 
  ditto, 
  between 
  base 
  

   of 
  coronal 
  ridge 
  and 
  the 
  sub-acute 
  posterior 
  angle, 
  39 
  mm. 
  

  

  S 
  

  

  

  /■ 
  

  

  