﻿VEBTEBEATES. 
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  shallow 
  basal 
  portion, 
  which 
  is 
  somewhat 
  expanded 
  posteriorly; 
  

   inner 
  margin 
  broadly 
  and 
  regularly 
  arched 
  round 
  the 
  base 
  of 
  the 
  

   coronal 
  prominence 
  from 
  the 
  obtuse 
  anterior 
  angle, 
  with 
  a 
  rather 
  

   deep 
  concave 
  course 
  in 
  the 
  region 
  of 
  the 
  posterior 
  depression, 
  join- 
  

   ing 
  the 
  posterior 
  border 
  in 
  a 
  subacute 
  angle, 
  inferiorly 
  inbeveled. 
  

   Coronal 
  ridge 
  prominent, 
  occupying 
  the 
  anterior 
  two-thirds 
  of 
  the 
  

   area, 
  and 
  culminating 
  in 
  the 
  broadly 
  rounded 
  crest 
  a 
  little 
  anterior 
  

   of 
  the 
  median 
  line; 
  anterior 
  slope 
  regularly 
  convex, 
  the 
  posterior 
  

   declivity 
  more 
  abruptly 
  descending 
  into 
  the 
  relatively 
  narrow 
  pos- 
  

   terior 
  depression, 
  which 
  is 
  defined 
  by 
  the 
  narrow, 
  moderately 
  up- 
  

   raised, 
  rounded 
  alate 
  lobe. 
  Surface 
  traversed 
  by 
  well-marked, 
  widely 
  

   spaced 
  transverse 
  furrows, 
  especially 
  noticeable 
  in 
  the 
  coronal 
  prom- 
  

   inence, 
  which 
  are 
  occupied 
  by 
  irregular 
  transversely 
  elongated 
  pores, 
  

   "Z& 
  *V 
  / 
  - 
  bolow 
  intervening 
  undulations 
  showing 
  minute, 
  widely 
  spaced 
  punctas. 
  

   Length 
  of 
  anterior 
  articular 
  border 
  at 
  least 
  17 
  mm 
  ; 
  breadth 
  across 
  

   the 
  inner 
  margin 
  20 
  mm. 
  

  

  The 
  unique 
  example 
  above 
  described 
  was 
  obtained 
  by 
  Maj. 
  Powell's 
  

   expedition 
  to 
  the 
  Grand 
  canon 
  of 
  .Colorado, 
  from 
  the 
  Carboniferous 
  

   limestone. 
  With 
  the 
  exception 
  or 
  the 
  outer 
  extremity, 
  the 
  specimen 
  

   is 
  quite 
  entire, 
  admitting 
  of 
  satisfactory 
  comparison 
  with 
  allied 
  forms. 
  

   Of 
  the 
  latter, 
  it 
  is, 
  perhaps, 
  most 
  intimately 
  related 
  to 
  Deltodus 
  cingu- 
  

   latus, 
  N. 
  and 
  W., 
  of 
  the 
  Chester 
  formation, 
  being 
  distinguished 
  chiefly 
  

   by 
  its 
  proportionately 
  greater 
  breadth 
  compared 
  to 
  the 
  length 
  of 
  the 
  

   tooth, 
  narrower 
  and 
  more 
  widely 
  spaced 
  transverse 
  sulci, 
  and 
  nar- 
  

   rower 
  alate 
  lobe. 
  It 
  also 
  differs 
  from 
  D. 
  Mercurii, 
  Newb., 
  in 
  the 
  

   same 
  respects 
  relating 
  to 
  the 
  diametral 
  dimensions 
  and 
  in 
  the 
  dis- 
  

   tinct 
  transverse 
  undulations 
  of 
  the 
  coronal 
  region, 
  — 
  indeed, 
  the 
  only 
  

   feature 
  which 
  it 
  shows 
  in 
  common 
  with 
  that 
  species 
  being 
  the 
  nar- 
  

   row 
  posterior 
  alation. 
  

  

  We 
  have 
  described 
  in 
  another 
  place, 
  under 
  the 
  specific 
  designation 
  

   Deltodus 
  propinquus, 
  a 
  fine 
  large 
  species 
  from 
  the 
  Coal 
  Measures 
  of 
  

   Illinois, 
  which, 
  so 
  far 
  as 
  relates 
  to 
  the 
  homologous 
  form, 
  bears 
  most 
  

   intimate 
  resemblance 
  with 
  the 
  present 
  tooth. 
  The 
  only 
  appreciable 
  

   distinctions 
  by 
  which 
  the 
  latter 
  teeth 
  may 
  be 
  distinguished 
  consist 
  

   in 
  the 
  greater 
  obliquity 
  of 
  the 
  inner 
  margin 
  and 
  the 
  undulations 
  

   traversing 
  the 
  crown, 
  — 
  indeed, 
  worn 
  examples, 
  in 
  which 
  the 
  longitu- 
  

   dinal 
  undulations 
  are 
  obsolete, 
  are 
  hardly 
  recognizable 
  from 
  the 
  tooth 
  

   above 
  described. 
  

  

  The 
  specific 
  designation 
  is 
  given 
  in 
  honor 
  of 
  Major 
  J. 
  W. 
  Powell, 
  

   U, 
  S. 
  Geologist, 
  in 
  charge 
  of 
  the 
  geographical 
  and 
  geological 
  explor- 
  

   ation 
  of 
  the 
  Bocky 
  Mountain 
  region. 
  The 
  unique 
  type 
  is 
  deposited 
  

  

  