﻿VEETEBEATES. 
  173 
  

  

  extremity 
  at 
  an 
  angle 
  of 
  about 
  25°. 
  A 
  large 
  example 
  of 
  the 
  trigo- 
  

   nal 
  form 
  measures 
  in 
  length 
  along 
  the 
  straight 
  border 
  31 
  mm. 
  ; 
  

   breadth 
  across 
  inner 
  margin 
  27 
  mm., 
  more 
  or 
  less 
  ; 
  lateral 
  borders 
  

   converge 
  at 
  angles 
  of 
  30° 
  to 
  40°. 
  

  

  The 
  above 
  notices 
  of 
  the 
  forms 
  associated 
  by 
  Professor 
  Agassiz 
  

   under 
  the 
  specific 
  designation 
  Tomoclus 
  convexus, 
  will, 
  perhaps, 
  also 
  

   serve 
  to 
  convey 
  a 
  tangible 
  idea 
  of 
  the 
  distinctively 
  generic 
  charac- 
  

   teristics 
  ascribable 
  to 
  the 
  genus 
  Tomodus. 
  Its 
  relations 
  are 
  most 
  

   intimate 
  'with 
  Xystroclus, 
  from 
  which 
  it 
  chiefly 
  differs 
  in 
  the 
  con- 
  

   spicuous 
  convexity 
  of 
  the 
  coronal 
  ridge, 
  the 
  extremely 
  abrupt 
  artic- 
  

   ular 
  border, 
  and 
  the 
  absence 
  of 
  transverse 
  disposition 
  of 
  the 
  punctae 
  

   of 
  the 
  triturating 
  surface. 
  Our 
  knowledge 
  of 
  the 
  genus 
  is 
  so 
  imper- 
  

   fect 
  that 
  we 
  may 
  have 
  overlooked 
  important 
  generic 
  characters, 
  

   which 
  the 
  specimens 
  themselves 
  might 
  reveal 
  at 
  a 
  glance. 
  Viewed 
  

   in 
  accordance 
  with 
  the 
  facts 
  elicited 
  from 
  the 
  data 
  within 
  reach, 
  

   we 
  are 
  led 
  to 
  suspect 
  some 
  confusion 
  exists 
  in 
  the 
  interpretations 
  

   of 
  the 
  limits 
  of 
  the 
  genus, 
  and 
  that 
  in 
  consequence 
  forms 
  have 
  been 
  

   referred 
  to 
  it 
  which 
  have 
  no 
  intimate 
  congeneric 
  relationship 
  with 
  

   Tomoclus 
  convexus. 
  Of 
  the 
  latter, 
  the 
  species 
  described 
  by 
  Dr. 
  

   L. 
  de 
  Koninck 
  in 
  his 
  great 
  work 
  on 
  the 
  Belgian 
  Carboniferous 
  

   limestone 
  fauna,* 
  under 
  the 
  names 
  Tomoclus 
  Craigi, 
  and 
  T. 
  lacini- 
  

   atus, 
  certainly 
  show 
  a 
  wide 
  departure 
  from 
  the 
  typical 
  species 
  

   T. 
  convexus, 
  Ag., 
  while 
  their 
  relations 
  with 
  Psephodus 
  are 
  strongly 
  

   suggested 
  to 
  judge 
  from 
  the 
  admirable 
  figures 
  illustrating 
  the 
  Bel- 
  

   gian 
  teeth. 
  The 
  specific 
  identity 
  of 
  the 
  two 
  forms 
  ascribed 
  to 
  

   T. 
  convexus 
  may 
  be 
  also 
  reasonably 
  questioned, 
  since 
  both 
  have 
  the 
  

   general 
  conformation 
  of 
  mandibular 
  teeth, 
  and 
  it 
  is 
  difficult 
  to 
  con- 
  

   ceive 
  how 
  they 
  could 
  have 
  been 
  associated 
  on 
  the 
  same 
  jaw. 
  

  

  The 
  American 
  form 
  mentioned 
  in 
  this 
  connection, 
  and 
  which 
  is 
  

   provisionally 
  referred 
  to 
  Tomodus, 
  is 
  the 
  sole 
  representative 
  of 
  the 
  

   genus 
  thus 
  far 
  brought 
  to 
  light 
  in 
  the 
  Carboniferous 
  formations 
  of 
  

   this 
  country. 
  The 
  genus 
  is 
  Carboniferous, 
  restricted 
  so 
  far 
  as 
  is 
  

   known 
  to 
  the 
  earlier 
  group 
  of 
  the 
  series. 
  

  

  Tomodus 
  ? 
  limit 
  aris, 
  St. 
  J. 
  and 
  W. 
  

  

  PI. 
  XIII, 
  Fig. 
  12. 
  

  

  Teeth 
  small, 
  longitudinally 
  elongate,-cuneiform 
  in 
  outline, 
  rather 
  

   strongly 
  arched 
  in 
  the 
  direction 
  of 
  inrollment. 
  Antero-lateral 
  bor- 
  

   der 
  gently 
  curved 
  sigmoidally 
  from 
  the 
  obtuse 
  inner 
  angle 
  to 
  the 
  

  

  $ 
  

  

  *Faune 
  du 
  calcaire 
  carbonifdre 
  de 
  la 
  Belgirfue, 
  Premiere 
  partie, 
  1878, 
  p. 
  

  

  60. 
  

  

  