﻿PYCNODONTID^. 
  207 
  

  

  being 
  four 
  scales, 
  of 
  which 
  the 
  first 
  two 
  are 
  described 
  and 
  

   figured 
  by 
  the 
  present 
  writer 
  in 
  Proc. 
  Geol. 
  Assoc, 
  vol. 
  ix. 
  

   (1890), 
  p. 
  297, 
  pi. 
  iii. 
  figs. 
  30, 
  31; 
  Stonesfield 
  Slate, 
  

   Stonesfield. 
  Egerton 
  6f 
  Ennishillen 
  Colls. 
  

  

  Mesodon 
  tenuidens, 
  A. 
  S. 
  Woodward. 
  

  

  1890. 
  Mesodon 
  tenuidens, 
  A. 
  S. 
  Woodward, 
  Proc. 
  Geol. 
  Assoc, 
  vol. 
  xi. 
  

   p. 
  300, 
  pi. 
  iii. 
  fig. 
  29 
  (erroneously 
  named 
  latidens 
  in 
  text). 
  

  

  Type. 
  Eight 
  splenial 
  dentition 
  ; 
  British 
  Museum. 
  

  

  A 
  small 
  species 
  known 
  only 
  by 
  the 
  splenial 
  dentition. 
  Teeth 
  

   finely 
  rugose, 
  with 
  a 
  transversely 
  elongated 
  apical 
  pit 
  ; 
  all 
  or 
  nearly 
  

   all 
  the 
  teeth 
  broader 
  than 
  long. 
  Principal 
  teeth 
  on 
  splenial 
  bone 
  

   at 
  least 
  twice 
  as 
  broad 
  as 
  long, 
  arched, 
  and 
  inwardly 
  tapering 
  ; 
  

   this 
  series 
  flanked 
  within 
  by 
  one 
  row, 
  and 
  externally 
  by 
  four 
  rows 
  

   of 
  small 
  teeth 
  passing 
  forwards 
  into 
  two 
  rows. 
  

  

  Form. 
  Sf 
  Loc. 
  Bathonian 
  : 
  Oxfordshire. 
  

  

  47983. 
  Type 
  specimen 
  ; 
  Stonesfield 
  Slate, 
  Stonesfield. 
  

  

  Presented 
  by 
  the 
  Hon. 
  Robert 
  Marsham, 
  1877. 
  

  

  Mesodon 
  lsevior, 
  Fricke. 
  

  

  1846. 
  Pycnodus 
  didymus, 
  G. 
  von 
  Minister 
  {errore), 
  Beitr. 
  Petrefakt. 
  

  

  pt. 
  vii. 
  p. 
  41, 
  pi. 
  ii. 
  fig. 
  26, 
  pi. 
  iii. 
  fig. 
  6. 
  

   (?) 
  1864. 
  Pycnodus 
  hugii, 
  H. 
  Credner 
  (errore), 
  Zeitschr. 
  deutsch. 
  geol. 
  

  

  Ges. 
  vol. 
  xvi. 
  p. 
  244, 
  pi. 
  xi. 
  fig. 
  7. 
  

   1875. 
  Mesodon 
  Icevior, 
  K. 
  Fricke, 
  Palseontogr. 
  vol. 
  xxii. 
  p. 
  364, 
  pi. 
  xix. 
  

  

  figs. 
  9-12, 
  pi. 
  xx. 
  figs. 
  1, 
  2. 
  

  

  Type. 
  Splenial 
  dentition. 
  

  

  A 
  species 
  of 
  moderate 
  or 
  large 
  size, 
  known 
  only 
  by 
  the 
  dentition. 
  

   Teeth 
  irregularly 
  rounded 
  in 
  outline, 
  with 
  an 
  apical 
  pit 
  very 
  shallow 
  

   in 
  the 
  principal 
  series, 
  and 
  with 
  feeble 
  radiating 
  rugae. 
  Yomerine 
  

   teeth 
  closely 
  arranged 
  ; 
  those 
  of 
  the 
  median 
  series 
  not 
  much 
  

   broader 
  than 
  long, 
  and 
  their 
  breadth 
  about 
  equalling 
  that 
  of 
  the 
  

   two 
  lateral 
  series 
  ; 
  outer 
  lateral 
  series 
  scarcely 
  smaller 
  than 
  the 
  

   inner, 
  and 
  often 
  flanked 
  by 
  an 
  incomplete 
  supplementary 
  row 
  of 
  

   minute 
  teeth. 
  Teeth 
  of 
  principal 
  series 
  on 
  splenial 
  bone 
  much 
  

   broader 
  than 
  long 
  and 
  inwardly 
  tapering 
  ; 
  flanked 
  within 
  by 
  one 
  

   continuous 
  and 
  one 
  incomplete 
  series 
  of 
  small 
  teeth 
  ; 
  and 
  flanked 
  

   externally 
  by 
  three 
  series, 
  of 
  which 
  the 
  inner 
  equals 
  the 
  outer 
  in 
  

   size, 
  and 
  the 
  median 
  is 
  sometimes 
  in 
  part 
  duplicated. 
  

  

  Form. 
  6f 
  Log. 
  Upper 
  Corallian 
  and 
  Kimmeridgian 
  : 
  Hanover. 
  1 
  

  

  1 
  The 
  fragments 
  from 
  the 
  Kimmeridgian 
  and 
  Portlandian 
  of 
  N. 
  France 
  

   ascribed 
  to 
  this 
  species 
  by 
  Sauvage 
  (Bull. 
  Soc. 
  Geol. 
  France, 
  [3] 
  vol. 
  viii. 
  1880, 
  

   p. 
  529, 
  pi. 
  xix. 
  fig. 
  4) 
  appear 
  to 
  be 
  incorrectly 
  determined. 
  

  

  