﻿VEETEBEATES. 
  185 
  

  

  the 
  upper 
  jaw. 
  The 
  latter 
  is 
  distinguished 
  by 
  its 
  elongate 
  subspat- 
  

   ulate 
  shape, 
  narrow 
  lateral 
  diameter 
  and 
  narrow 
  alation, 
  less 
  rapidly 
  

   converging 
  lateral 
  borders 
  and 
  more 
  oblique 
  direction 
  of 
  the 
  poste- 
  

   rior 
  portion 
  of 
  the 
  inner 
  margin, 
  relatively 
  greater 
  extent 
  of 
  the 
  

   articular 
  edge 
  of 
  the 
  antero-lateral 
  border, 
  (both 
  borders 
  being 
  much 
  

   as 
  in 
  the 
  same 
  form 
  of 
  the 
  representative 
  Keokuk 
  species, 
  S. 
  Icevis- 
  

   simus,) 
  and 
  the 
  more 
  uniform 
  coronal 
  contour, 
  which 
  does 
  not 
  pre- 
  

   sent 
  to 
  the 
  same 
  extent 
  the 
  strongly 
  developed 
  ridges 
  characteristic 
  

   of 
  the 
  opposed 
  mandibular 
  teeth. 
  In 
  all, 
  as 
  also 
  in 
  the 
  teeth 
  sup- 
  

   posed 
  to 
  represent 
  the 
  mandibular 
  median 
  form, 
  the 
  coronal 
  punc- 
  

   tation 
  is 
  essentially 
  the 
  same, 
  being 
  relatively 
  fine, 
  closely 
  set, 
  and 
  

   showing 
  a 
  tendency 
  to 
  elongation 
  in 
  the 
  longitudinal 
  direction 
  of 
  the 
  

   tooth, 
  although 
  very 
  variable 
  in 
  this 
  respect 
  according 
  to 
  the 
  condi- 
  

   tion 
  of 
  preservation 
  of 
  the 
  coronal 
  surface. 
  

  

  Mandibular 
  median 
  teeth 
  distinguished 
  by 
  their 
  triangular 
  outline, 
  

   rather 
  strongly 
  arched 
  from 
  within 
  outward 
  and 
  strongly 
  inrolled 
  at 
  

   the 
  outer 
  extremity. 
  Postero-lateral 
  border 
  nearly 
  straight, 
  defined 
  

   above 
  by 
  the 
  rounded 
  enamel 
  fold, 
  basal 
  portion 
  channeled 
  and 
  

   beveled 
  interiorly 
  to 
  an 
  obtuse 
  edge 
  ; 
  antero-lateral 
  border 
  very 
  ob- 
  

   lique, 
  rapidly 
  converging 
  from 
  the 
  subacute 
  inner 
  angle 
  to 
  point 
  of 
  

   inrollment 
  forming 
  an 
  angle 
  of 
  40° 
  to 
  50° 
  with 
  the 
  opposite 
  side, 
  

   basal 
  portion 
  beneath 
  the 
  enamel 
  fold 
  somewhat 
  channeled 
  and 
  bev- 
  

   eled, 
  merging 
  into 
  the 
  thickened 
  edge 
  that 
  defines 
  this 
  side 
  of 
  the 
  

   tooth; 
  inner 
  margin 
  making 
  nearly 
  a 
  right 
  angle 
  with 
  the 
  postero- 
  

   lateral 
  border, 
  gently 
  arched 
  and 
  somewhat 
  more 
  sharply 
  rounded 
  near 
  

   the 
  posterior 
  angle, 
  worn 
  specimens 
  inbevelecl 
  interiorly. 
  Crown 
  

   transversely 
  nearly 
  plane, 
  slightly 
  arched 
  near 
  the 
  postero-lateral 
  

   l 
  border 
  into 
  the 
  low, 
  obscurely 
  defined 
  coronal 
  prominence 
  ; 
  enamel 
  sur- 
  

   face 
  near 
  inner 
  margin 
  marked 
  by 
  more 
  or 
  less 
  distinct 
  lines 
  of 
  

   growth 
  parallel 
  with 
  the 
  inner 
  margin, 
  also 
  faint 
  longitudinal 
  plica? 
  ; 
  

   worn 
  surface 
  exhibiting 
  the 
  usual 
  minute, 
  closely 
  arranged 
  puncta- 
  

   tion 
  characteristic 
  of 
  the 
  associated 
  forms 
  of 
  the 
  species. 
  Inferior 
  

   surface 
  moderately 
  excavated, 
  smooth, 
  conforming 
  in 
  a 
  general 
  way 
  

   with 
  the 
  contour 
  of 
  the 
  coronal 
  region. 
  A 
  small 
  individual 
  measures 
  in 
  

   jostero-lateral 
  border 
  across 
  the 
  inner 
  margin 
  10.5 
  mm. 
  ; 
  length 
  along 
  , 
  

   transverse 
  diameter 
  to 
  point 
  of 
  inrollment 
  6.5 
  mm. 
  A 
  large-sized 
  

   tooth 
  is 
  respectively29 
  mm. 
  and 
  21 
  mm. 
  in 
  breadth 
  and 
  length. 
  

  

  Compared 
  with 
  the 
  corresponding 
  form 
  of 
  S. 
  Icevissimus, 
  of 
  the 
  

   Keokuk 
  limestone, 
  the 
  mandibular 
  median 
  teeth 
  of 
  the 
  present 
  

   species 
  are 
  distinguished 
  by 
  their 
  less 
  oblique 
  antero-lateral 
  border 
  

   and 
  spirally 
  inrolled 
  outer 
  extremity, 
  and 
  smoother 
  coronal 
  surface. 
  

  

  