﻿VEETEBEATES. 
  95 
  

  

  oblique 
  anterolateral 
  border 
  rapidly 
  converging 
  toward 
  the 
  outer 
  

   extremity, 
  which 
  presents 
  the 
  same 
  degree 
  of 
  inrollment 
  observed 
  

   in 
  the 
  preceding 
  posterior 
  form. 
  Coronal 
  region 
  presenting 
  a 
  series 
  

   of 
  transverse 
  ridges, 
  which 
  individually 
  possess 
  coronal 
  characters 
  

   ascribable 
  to 
  certain 
  forms 
  of 
  Helodus, 
  a 
  medium-size 
  specimen 
  

   showing 
  five 
  such 
  coronal 
  ridges, 
  whose 
  longer 
  axes 
  correspond 
  to 
  

   longer 
  diameter 
  Of 
  the 
  posterior 
  tooth. 
  The 
  individual 
  ridges 
  rise 
  in 
  

   an 
  even 
  convex 
  surface 
  behind, 
  culminating 
  in 
  an 
  obtuse 
  even 
  crest, 
  

   the 
  outer 
  face 
  moderately 
  concave 
  vertically, 
  and 
  invested 
  in 
  the 
  

   enamel 
  layer, 
  save 
  along 
  the 
  crests, 
  which 
  reveal 
  the 
  relatively 
  

   coarse 
  punctate 
  structure. 
  Breadth 
  of 
  series 
  across 
  inner 
  margin 
  10 
  

   m 
  m. 
  ; 
  length 
  along 
  postero-lateral 
  border 
  11 
  mm., 
  corresponding 
  to 
  

   that 
  of 
  the 
  anterior 
  border 
  of 
  the 
  posterior 
  tooth. 
  The 
  proportionate 
  

   dimensions 
  of 
  the 
  individual 
  coronal 
  ridges 
  are 
  represented 
  in 
  the 
  

   illustrations. 
  

  

  Of 
  the 
  forms 
  above 
  noticed 
  and 
  associated 
  under 
  the 
  same 
  specific 
  

   designation, 
  the 
  collections 
  contain 
  a 
  fair 
  suite 
  of 
  representatives, 
  

   amongst 
  which 
  the 
  teeth 
  referred 
  to 
  the 
  posterior 
  position 
  upon 
  the 
  

   lower 
  jaw 
  are 
  in 
  about 
  double 
  the 
  numbers 
  of 
  those 
  belonging 
  to 
  

   the 
  maxillaries 
  ; 
  while 
  of 
  the 
  small 
  anterior, 
  or 
  median 
  dental 
  series 
  

   of 
  the 
  upper 
  jaw, 
  only 
  a 
  single 
  specimen 
  is 
  known 
  — 
  that 
  discovered 
  

   by 
  Mr. 
  Wachsmuth, 
  at 
  Danville, 
  Iowa. 
  With 
  regard 
  to 
  the 
  latter, 
  

   the 
  resemblance 
  it 
  bears 
  to 
  Helodus 
  elytra, 
  N. 
  and 
  W., 
  of 
  the 
  same 
  

   geological 
  horizon, 
  creates 
  a 
  suspicion 
  of 
  the 
  specific 
  identity 
  of 
  

   similar 
  Helodus-like 
  teeth 
  with 
  the 
  form 
  here 
  alluded 
  to. 
  The 
  

   original 
  specimen 
  of 
  Helodus 
  elytra, 
  however, 
  apparently 
  shows 
  a 
  

   series 
  of 
  independent, 
  contiguous 
  teeth, 
  in 
  their 
  relative 
  natural 
  

   position, 
  but 
  with 
  their 
  coronal 
  crests 
  worn 
  down 
  almost 
  even 
  with 
  

   the 
  basal 
  margins, 
  so 
  that 
  it 
  is 
  impossible 
  to 
  determine 
  the 
  coronal 
  

   contour, 
  although, 
  as 
  has 
  been 
  stated, 
  we 
  strongly 
  suspect 
  the 
  form 
  

   is 
  identical 
  with 
  teeth, 
  perfect 
  specimens 
  of 
  which 
  have 
  been 
  de- 
  

   scribed 
  under 
  other 
  designations. 
  The 
  consolidation 
  along 
  the 
  basal 
  

   impingement 
  of 
  the 
  separate 
  teeth 
  is 
  precisely 
  what 
  has 
  been 
  noticed 
  

   in 
  connection 
  with 
  other 
  allied 
  forms 
  of 
  this 
  family, 
  and 
  although 
  a 
  

   matter 
  of 
  biological 
  interest 
  and 
  importance, 
  it 
  should 
  not 
  militate 
  

   against 
  the 
  recognition 
  of 
  the 
  specific 
  identity 
  of 
  series 
  of 
  isolated 
  

   teeth 
  and 
  those 
  that 
  are 
  joined 
  by 
  their 
  bases 
  into 
  a 
  solid 
  dental 
  

   plate, 
  as 
  is 
  the 
  case 
  in 
  the 
  above 
  form. 
  

  

  The 
  maxillary 
  posterior 
  teeth 
  are 
  seldom 
  preserved 
  entire, 
  and 
  the 
  

   attenuation 
  of 
  the 
  anterior 
  region 
  exhibits 
  unmistakable 
  evidences 
  

   of 
  the 
  excessive 
  attrition 
  these 
  teeth 
  were 
  subjected 
  to 
  during 
  the 
  life 
  

  

  