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  VEBTEBEATES. 
  123 
  

  

  terminating 
  in 
  the 
  more 
  or 
  less 
  produced, 
  acutely 
  rounded 
  posterior 
  

   extremity; 
  inner 
  margin 
  making 
  two 
  broad 
  arches, 
  the 
  larger 
  in 
  

   rounding 
  the 
  base 
  of 
  the 
  postero/coronal 
  prominence, 
  the 
  lesser 
  in 
  

   skirting 
  the 
  anterior 
  prominence 
  on 
  the 
  way 
  to 
  the 
  obtuse 
  anterior 
  

   angle, 
  in 
  ordinarily 
  preserved 
  teeth 
  inbeveled 
  inferiorly. 
  Coronal 
  

   contour 
  typical 
  of 
  the 
  corresponding 
  form 
  of 
  the 
  genus, 
  divided 
  into 
  

   two 
  principal 
  regions 
  occupied 
  respectively 
  by 
  the 
  posterior 
  lobe 
  and 
  

   the 
  narrower 
  anterior 
  prominence. 
  The 
  posterior 
  prominence 
  cul- 
  

   minates 
  about 
  one-fourth 
  the 
  distance 
  from 
  the 
  shallow 
  sulcus 
  

   forming 
  the 
  demarkation 
  between 
  the 
  coronal 
  elevations, 
  the 
  

   anterior 
  acclivity 
  rising 
  quite 
  steeply 
  into 
  the 
  obtusely 
  rounded 
  

   crest, 
  whence 
  the 
  surface 
  much 
  more 
  gently 
  declines 
  in 
  a 
  slight 
  

   concavity 
  to 
  the 
  postero 
  -lateral 
  border, 
  where 
  the 
  enamel 
  forms 
  a 
  

   narrow 
  fold 
  distinctly 
  defined 
  from 
  the 
  basal 
  portions; 
  anterior 
  

   lobe 
  more 
  regularly 
  and 
  gently 
  arched 
  transversely, 
  the 
  longitudinal 
  

   axis 
  lying 
  near 
  the 
  median 
  depression 
  with 
  a 
  narrow 
  steep 
  slope 
  

   on 
  that 
  side, 
  the 
  wide, 
  gentle 
  anterior 
  slope 
  being 
  interrupted 
  by 
  

   more 
  or 
  less 
  distinct 
  revolving 
  furrows, 
  margined 
  along 
  the 
  antero- 
  

   lateral 
  border 
  by 
  a 
  narrow 
  plane 
  belt 
  defined 
  from 
  the 
  anterior 
  

   prominence 
  by 
  a 
  slight 
  impressed 
  line, 
  the 
  coronal 
  enamel 
  forming 
  

   a 
  very 
  narrow 
  fold 
  along 
  the 
  antero-lateral 
  border. 
  Greatest 
  

   breadth 
  of 
  medium-size 
  tooth 
  across 
  inner 
  margin 
  21 
  mm.; 
  length 
  

   of 
  antero-lateral 
  border 
  to 
  inrolled 
  outer 
  margin 
  8 
  mm. 
  ; 
  greatest 
  

   length 
  along 
  crest 
  of 
  posterior 
  lobe 
  13 
  mm.; 
  position 
  of 
  median 
  

   depression 
  a 
  little 
  anterior 
  of 
  a 
  line 
  drawn 
  through 
  the 
  centre 
  of 
  the 
  

   tooth. 
  A 
  large 
  size 
  specimen 
  in 
  the 
  collection 
  of 
  Mr. 
  Van 
  Home, 
  

   from 
  Alton, 
  is 
  quite 
  one-third 
  larger 
  than 
  that 
  indicated 
  in 
  the 
  

   above 
  measurements. 
  

  

  Although 
  the 
  collections 
  afford 
  no 
  positive 
  evidence 
  of 
  the 
  specific 
  

   identity 
  of 
  the 
  dental 
  elements 
  belonging 
  to 
  the 
  anterior 
  extremity 
  

   of 
  the 
  upper 
  jaw 
  of 
  the 
  present 
  species, 
  there 
  is, 
  however, 
  a 
  well 
  

   represented 
  form 
  of 
  teeth 
  occurring 
  in 
  series 
  precisely 
  after 
  the 
  

   Helodus-like 
  teeth 
  associated 
  with 
  the 
  magnificent 
  group 
  of 
  teeth 
  

   furnishing 
  the 
  basis 
  for 
  the 
  description 
  of 
  the 
  species 
  Chitonodus 
  

   latus, 
  (Leidy 
  sp.) 
  (Cochlijdus 
  nobilis, 
  N. 
  and 
  W.). 
  More 
  frequently 
  

   occurring 
  as 
  isolated 
  teeth, 
  examples 
  of 
  two 
  or 
  more 
  teeth 
  occupy- 
  

   ing 
  their 
  natural 
  relative 
  position 
  in 
  deltoid 
  series 
  have 
  been 
  ob- 
  

   tained, 
  so 
  that 
  little 
  doubt 
  can 
  be 
  entertained 
  as 
  to 
  their 
  relations 
  

   with 
  some 
  Cochliodont, 
  probably 
  to 
  the 
  species 
  herein 
  mentioned. 
  

   Teeth 
  occurring 
  in 
  series 
  of 
  two 
  or 
  more 
  individuals, 
  together 
  form- 
  

   ing 
  a 
  deltoid 
  figure, 
  narrowing 
  from 
  within 
  outward, 
  and 
  presenting 
  

  

  