﻿PYCNODONTID^;. 
  

  

  245 
  

  

  vomer 
  depressed 
  and 
  flattened, 
  conspicuously 
  rugose, 
  those 
  of 
  the 
  

   median 
  series 
  not 
  very 
  prominent 
  and 
  at 
  least 
  equalling 
  in 
  width 
  

   the 
  two 
  flanking 
  series. 
  

  

  Form. 
  <Sf 
  Loc. 
  Jurassic 
  : 
  Eussia. 
  

  

  P. 
  3782. 
  Type 
  specimen 
  described 
  and 
  figured 
  by 
  Mantell, 
  loc. 
  cit. 
  ; 
  

   from 
  Ejeff, 
  on 
  the 
  Volga. 
  The 
  crowns 
  of 
  the 
  outermost 
  

   series 
  of 
  teeth 
  are 
  all 
  broken 
  away, 
  and 
  only 
  one 
  of 
  the 
  

   median 
  series 
  remains. 
  Enniskillen 
  Coll. 
  

  

  Gyrodus 
  (?) 
  cretaceus, 
  Agassiz. 
  

  

  1833-39. 
  Sphcerodus 
  mammillaris, 
  L. 
  Agassiz, 
  Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  i. 
  

  

  p. 
  15 
  (in 
  part), 
  pi. 
  lxxiii. 
  figs. 
  1, 
  2. 
  [Teeth.] 
  

   1839-44. 
  Gyrodus 
  cretaceus, 
  L. 
  Agassiz, 
  ibid. 
  vol. 
  ii. 
  pt. 
  ii. 
  p. 
  233, 
  

  

  pi. 
  lxix. 
  a. 
  fig. 
  13. 
  

   1840. 
  Gyrodus 
  cretaceus, 
  R. 
  Owen, 
  Odontography, 
  p. 
  72. 
  

   1844. 
  Gyrodus 
  mammillaris, 
  L. 
  Agassiz, 
  ibid. 
  vol. 
  ii. 
  pt. 
  ii. 
  p. 
  236. 
  

   1844. 
  Bycnodus 
  marginalis, 
  L. 
  Agassiz, 
  ibid. 
  vol. 
  ii. 
  pt. 
  ii. 
  p. 
  199. 
  

  

  [Tooth.] 
  

   1850. 
  Gyrodus 
  cretaceus, 
  F. 
  Dixon, 
  Geol. 
  Sussex, 
  p. 
  370, 
  pi. 
  xxx. 
  fig. 
  15. 
  

   1850. 
  Gyrodus 
  conicus, 
  F. 
  Dixon, 
  ibid. 
  p. 
  370, 
  pi. 
  xxxii. 
  fig. 
  8. 
  

   1888. 
  Gyrodus 
  cretaceus, 
  A. 
  S. 
  Woodward, 
  Proc. 
  Geol. 
  Assoc, 
  vol. 
  x. 
  

  

  p. 
  308. 
  

  

  Type. 
  Portion 
  of 
  vomerine 
  dentition. 
  

  

  A 
  large 
  species 
  of 
  uncertain 
  genus, 
  probably 
  not 
  Gyrodus, 
  but 
  

   known 
  only 
  by 
  fragmentary 
  dentition. 
  Dental 
  crowns 
  much 
  elevated, 
  

   obtusely 
  acuminate, 
  and 
  coarsely 
  rugose 
  ; 
  those 
  of 
  the 
  median 
  and 
  

   outer 
  paired 
  series 
  on 
  the 
  vomer 
  longer 
  than 
  broad, 
  about 
  equal 
  in 
  

   size 
  ; 
  teeth 
  of 
  inner 
  paired 
  series 
  on 
  this 
  bone 
  relatively 
  small 
  and 
  

   irregularly 
  subdivided. 
  

  

  Form. 
  Sf 
  Loc. 
  Senonian 
  : 
  Sussex 
  and 
  Surrey. 
  

  

  39048. 
  Vomerine 
  dentition 
  figured 
  in 
  Dixon's 
  Geol. 
  Sussex, 
  pi. 
  xxx. 
  

   fig. 
  15 
  ; 
  Chalk, 
  Lewes. 
  Boiuerbank 
  Coll. 
  

  

  49802. 
  Portion 
  of 
  vomerine 
  dentition 
  ; 
  Upper 
  Chalk, 
  St. 
  Catherine's 
  

   Hill 
  Pit, 
  near 
  Guildford. 
  Capron 
  Coll. 
  

  

  P. 
  6852. 
  Portion 
  apparently 
  of 
  splenial 
  dentition, 
  showing 
  principal 
  

  

  series 
  of 
  teeth 
  ; 
  Chalk, 
  Upper 
  Warlingham, 
  near 
  Croydon. 
  

  

  Presented 
  by 
  G. 
  E. 
  Dibley, 
  Esq., 
  1893. 
  

  

  The 
  following 
  specimen 
  seems 
  to 
  belong 
  to 
  Gyrodus, 
  but 
  is 
  not 
  

   specifically 
  determined 
  : 
  — 
  

  

  43285. 
  Portion 
  of 
  relatively 
  broad 
  vomer, 
  with 
  well-spaced 
  teeth 
  

   remarkably 
  uniform 
  in 
  size 
  (PI. 
  XVII. 
  fig. 
  5) 
  ; 
  Kimmeridge 
  

  

  