﻿226 
  ACTINOPTERTGII. 
  

  

  P. 
  4694. 
  Imperfect 
  fish, 
  displaying 
  the 
  expansion 
  at 
  the 
  inferior 
  

   end 
  of 
  the 
  problematical 
  bone 
  (? 
  ridge 
  scnte) 
  at 
  the 
  hinder 
  

   extremity 
  of 
  the 
  body-cavity 
  ; 
  Cirin. 
  Purchased, 
  1884. 
  

  

  Microdon 
  egertoni 
  (Thiolliere). 
  

  

  1854. 
  Pycnodus 
  egertoni, 
  V. 
  Thiolliere, 
  Poiss. 
  Foss. 
  Bugey, 
  pt. 
  i. 
  p. 
  24, 
  

  

  with 
  figure. 
  

   1856. 
  Microdon 
  egertoni, 
  J. 
  J. 
  Heckel, 
  Denkschr. 
  k. 
  Akad. 
  Wiss. 
  

  

  math.-naturw. 
  CI. 
  vol. 
  xi. 
  p. 
  201. 
  

   1860. 
  Microdon 
  egertoni, 
  A. 
  Wagner, 
  Gelehrte 
  Anzeig. 
  k. 
  bay. 
  Akad. 
  

  

  vol. 
  1. 
  p. 
  396. 
  

  

  Type. 
  Nearly 
  complete 
  fish 
  ; 
  Lyons 
  Museum. 
  

  

  A 
  small 
  form 
  of 
  Microdon, 
  not 
  yet 
  satisfactorily 
  distinguished 
  

   from 
  the 
  type 
  species. 
  It 
  is 
  stated 
  to 
  differ 
  in 
  not 
  exhibiting 
  an 
  

   angulation 
  of 
  the 
  frontal 
  profile 
  and 
  in 
  having 
  fewer 
  vertebrae 
  ; 
  

   but 
  the 
  first 
  character 
  may 
  be 
  due 
  to 
  imperfect 
  preservation, 
  and 
  

   the 
  second 
  is 
  difficult 
  to 
  observe 
  with 
  certainty. 
  

  

  Form. 
  6f 
  Loc. 
  Lower 
  Kimmeridgian 
  (Lithographic 
  Stone) 
  : 
  Ain, 
  

   France. 
  

  

  P. 
  1637. 
  Imperfect, 
  crushed 
  specimen 
  0-13 
  in 
  length, 
  shown 
  for 
  

   the 
  most 
  part 
  in 
  impression 
  ; 
  Cirin. 
  Egerton 
  Coll. 
  

  

  P. 
  4895. 
  Slightly 
  larger 
  specimen 
  displaying 
  the 
  pelvic 
  and 
  median 
  

   fins, 
  but 
  wanting 
  the 
  greater 
  part 
  of 
  the 
  head 
  ; 
  Cirin. 
  

  

  Purchased, 
  1884. 
  

  

  Microdon 
  sauvanausi 
  (Thiolliere). 
  

   1850. 
  Pycnodus 
  sauvanausi, 
  V. 
  Thiolliere, 
  Ann. 
  Soc. 
  Sci. 
  Phys. 
  & 
  Nat. 
  

  

  Lyon, 
  [2] 
  vol. 
  iii. 
  p. 
  131. 
  

   1854. 
  Pycnodus 
  sauvanausii, 
  V. 
  Thiolliere, 
  Poiss. 
  Foss. 
  Bugey, 
  pt. 
  i. 
  

  

  p. 
  15, 
  with 
  plate. 
  

   1856. 
  Microdon 
  sauvanausii, 
  J. 
  J. 
  Heckel, 
  Denkschr. 
  k. 
  Akad. 
  Wiss., 
  

  

  math.-naturw. 
  CI. 
  vol. 
  xi. 
  p. 
  201. 
  

  

  Type. 
  Nearly 
  complete 
  fish 
  ; 
  Lyons 
  Museum. 
  

  

  A 
  large 
  species 
  attaining 
  a 
  length 
  of 
  about 
  0*6. 
  Maximum 
  depth 
  

   of 
  trunk 
  apparently 
  equalling 
  about 
  half 
  of 
  the 
  length 
  of 
  the 
  head 
  

   and 
  trunk 
  without 
  caudal 
  fin 
  ; 
  head 
  with 
  opercular 
  apparatus 
  

   occupying 
  somewhat 
  more 
  than 
  one-quarter 
  of 
  the 
  total 
  length 
  of 
  

   the 
  fish. 
  Each 
  premaxilla 
  with 
  two 
  chisel-shaped 
  teeth; 
  [other 
  

   teeth 
  imperfectly 
  known]. 
  Scales 
  apparently 
  confined 
  to 
  the 
  most 
  

   anterior 
  part 
  of 
  the 
  trunk. 
  

  

  A 
  fish 
  from 
  Cirin 
  described 
  as 
  intermediate 
  between 
  this 
  and 
  the 
  

  

  