﻿PYCNODONTnWE. 
  215 
  

  

  splenial 
  from 
  Yonne, 
  Prance 
  (H. 
  E. 
  Sauvage, 
  Bull. 
  Soc. 
  Sci. 
  Nat. 
  

   Yonne, 
  vol. 
  xxxiii. 
  pt. 
  ii. 
  1879, 
  p. 
  35, 
  pi. 
  ii. 
  fig. 
  5) 
  ; 
  an 
  imperfect 
  

   splenial 
  from 
  the 
  Lower 
  IS"eocomian 
  of 
  Ville-sur-Saulx, 
  Meuse, 
  

   France 
  (J. 
  Cornuel, 
  Bull. 
  Soc. 
  Geol. 
  Prance, 
  [3] 
  vol. 
  viii. 
  1880, 
  

   p. 
  158, 
  and 
  ibid. 
  [3] 
  vol. 
  xi. 
  1883, 
  p. 
  24, 
  pi. 
  i. 
  fig. 
  10) 
  ; 
  and 
  frag- 
  

   ments 
  from 
  the 
  phosphates 
  of 
  Cambridgeshire 
  and 
  Bedfordshire 
  

   (W. 
  Keeping, 
  Foss. 
  Xeocom. 
  Upware, 
  1883, 
  p. 
  82, 
  pi. 
  i. 
  fig. 
  5). 
  

  

  To 
  Mesodon 
  may 
  also 
  probably 
  be 
  referred 
  the 
  portions 
  of 
  vome- 
  

   rine 
  dentition 
  from 
  the 
  Corallian 
  of 
  Schnaitheini, 
  Wiirtemberg, 
  

   described 
  under 
  the 
  names 
  of 
  Tyjpodus 
  annulatus 
  and 
  splendens 
  by 
  

   F. 
  A. 
  Quenstedt, 
  Der 
  Jura 
  (1858), 
  p. 
  781, 
  pi. 
  xcvi. 
  figs. 
  16-18. 
  

   A 
  fragment 
  of 
  a 
  similar 
  vomer 
  is 
  ascribed 
  to 
  Sphcerodus 
  by 
  F. 
  A. 
  

   Quenstedt, 
  Handb. 
  Paheont. 
  (1852) 
  p. 
  214, 
  pi. 
  xvi. 
  fig. 
  9. 
  

  

  The 
  undefined 
  name 
  of 
  Pycnodus 
  tristycliius 
  (L. 
  Agassiz, 
  Poiss. 
  

   Foss. 
  vol. 
  ii. 
  pt. 
  ii. 
  1844, 
  p. 
  199) 
  seems 
  to 
  have 
  been 
  given 
  to 
  an 
  

   English 
  Jurassic 
  jaw 
  of 
  Mesodon, 
  probably 
  from 
  the 
  Stonesfield 
  

   Slate. 
  The 
  type 
  specimen 
  was 
  originally 
  in 
  the 
  Bristol 
  Museum. 
  

  

  The 
  following 
  form 
  of 
  dentition 
  seems 
  to 
  be 
  related 
  to 
  Mesodon, 
  

   but 
  is 
  not 
  represented 
  in 
  the 
  Collection 
  : 
  — 
  

  

  Gyronchus 
  oblongus, 
  L. 
  Agassiz, 
  Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  ii. 
  (1844) 
  

   p. 
  202, 
  pi. 
  lx. 
  a, 
  figs. 
  10, 
  11. 
  Gyronchus 
  (Sca_p7iodus) 
  

   oblongus, 
  L. 
  Agassiz, 
  ibid. 
  vol. 
  i. 
  (1844), 
  p. 
  xlii. 
  Sca- 
  

   pliodus 
  lieteromorphus, 
  J. 
  Morris 
  (" 
  ex 
  Agassiz, 
  MS."), 
  

   Catal. 
  Brit. 
  Foss. 
  (1854), 
  p. 
  344 
  ; 
  A. 
  S. 
  Woodward, 
  Proc. 
  

   Geol. 
  Assoc, 
  vol. 
  xi. 
  (1890), 
  p. 
  301, 
  pi. 
  iii. 
  figs. 
  33, 
  34. 
  

   Mesodon 
  oblongus. 
  Woodward 
  & 
  Sherborn, 
  Catal. 
  Brit. 
  

   Foss. 
  Yertebrata 
  (1890), 
  p. 
  120.— 
  Stonesfield 
  Slate; 
  

   Stonesfield. 
  [Yomer 
  ; 
  Bristol 
  Museum.] 
  

  

  Genus 
  ATHRODON, 
  Sauvage. 
  

   [Bull. 
  Soc. 
  Geol. 
  France, 
  [3] 
  vol. 
  viii. 
  1880, 
  p. 
  530.] 
  

  

  An 
  imperfectly 
  definable 
  genus, 
  known 
  only 
  by 
  the 
  splenial 
  bone, 
  

   which 
  much 
  resembles 
  that 
  of 
  Mesodon, 
  but 
  is 
  considerably 
  stouter 
  

   and 
  exhibits 
  a 
  remarkably 
  deep 
  symphysial 
  facette. 
  Splenial 
  teeth 
  

   as 
  in 
  Mesodon, 
  but 
  usually 
  much 
  more 
  irregularly 
  arranged, 
  and 
  

   the 
  principal 
  longitudinal 
  series 
  not 
  well 
  differentiated. 
  

  

  Athrodon 
  douvillei, 
  Sauvage. 
  

  

  1880. 
  Athrodon 
  douvillei, 
  H. 
  E. 
  Sauvage, 
  Bull. 
  Soc. 
  G6ol. 
  France, 
  [3] 
  

   vol. 
  Tiii. 
  p. 
  530, 
  pi. 
  xix. 
  fig. 
  5. 
  

  

  Type. 
  Left 
  splenial 
  ; 
  School 
  of 
  Mines, 
  Paris. 
  

  

  The 
  type 
  species. 
  Splenial 
  bone 
  longer 
  than 
  broad, 
  with 
  very 
  

  

  