﻿PYCNODONTID^}. 
  225 
  

  

  without 
  caudal 
  fin; 
  rostrum 
  prominent, 
  and 
  head 
  with 
  opercular 
  

   apparatus 
  occupying 
  somewhat 
  less 
  than 
  one-quarter 
  of 
  the 
  total 
  

   length 
  of 
  the 
  fish. 
  Vertebral 
  axis 
  at 
  origin 
  of 
  dorsal 
  fin 
  midway 
  

   between 
  the 
  dorsal 
  and 
  ventral 
  borders 
  of 
  the 
  fish. 
  Principal 
  

   series 
  of 
  mandibular 
  teeth 
  much 
  wider 
  than 
  the 
  two 
  outer 
  series, 
  of 
  

   which 
  the 
  innermost 
  is 
  insignificant. 
  Dorsal 
  fin 
  occupying 
  con- 
  

   siderably 
  more 
  than 
  half 
  of 
  the 
  back, 
  much 
  more 
  elevated 
  than 
  the 
  

   anal 
  fin, 
  which 
  is 
  also 
  shorter. 
  Ridge-scales 
  delicate 
  on 
  the 
  back, 
  

   robust 
  but 
  feebly 
  serrated 
  on 
  the 
  ventral 
  border 
  ; 
  flank-scales 
  

   ornamented 
  with 
  delicate 
  radiating 
  rugae. 
  

  

  Form. 
  Sf 
  Log. 
  Lower 
  Kimmeridgian 
  (Lithographic 
  Stone) 
  : 
  Ain, 
  

   Prance, 
  and 
  (?) 
  Bavaria. 
  

  

  P. 
  1635. 
  A 
  typical 
  specimen 
  in 
  counterpart, 
  much 
  disturbed 
  ; 
  Cirin, 
  

   Ain. 
  Egerton 
  Colh 
  

  

  P. 
  4693. 
  Imperfect 
  trunk 
  ; 
  Cirin. 
  Purchased, 
  1884. 
  

  

  49132. 
  Plaster 
  cast 
  of 
  a 
  small 
  fish, 
  probably 
  of 
  this 
  species 
  ; 
  Kel- 
  

   heim, 
  Bavaria. 
  Purchased, 
  1878. 
  

  

  Microdcm 
  wagneri 
  (Thiolliere). 
  

  

  1854. 
  Pycnodus 
  wagneri, 
  V. 
  Thiolliere, 
  Poiss. 
  Foss. 
  Bugey, 
  pt. 
  i. 
  p. 
  23, 
  

  

  with 
  figure. 
  

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

  

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

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

  

  Wiss. 
  vol. 
  1. 
  p. 
  396. 
  

  

  Type. 
  Nearly 
  complete 
  fish 
  ; 
  Lyons 
  Museum. 
  

  

  A 
  species 
  resembling 
  the 
  type 
  in 
  size, 
  general 
  form, 
  and 
  pro- 
  

   portions, 
  and 
  apparently 
  only 
  differing 
  in 
  the 
  extension 
  of 
  the 
  

   squamation 
  over 
  the 
  middle 
  of 
  the 
  flank 
  of 
  the 
  anterior 
  half 
  of 
  

   the 
  caudal 
  region. 
  

  

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

   France. 
  

  

  P. 
  1636. 
  A 
  fine 
  specimen 
  0*25 
  in 
  length 
  preserved 
  in 
  impression 
  

   and 
  wanting 
  the 
  rostral 
  portion 
  of 
  the 
  skull 
  ; 
  Cirin. 
  The 
  

   ribs 
  of 
  the 
  scales 
  originally 
  on 
  the 
  flanks 
  of 
  the 
  caudal 
  

   region 
  are 
  indicated 
  ; 
  and 
  the 
  form 
  of 
  the 
  hinder 
  part 
  of 
  

   the 
  trunk 
  suggests 
  that 
  the 
  figured 
  type 
  specimen 
  has 
  

   been 
  somewhat 
  distorted 
  by 
  crushing 
  in 
  that 
  region. 
  

  

  Egerton 
  Coll. 
  

   part 
  in. 
  o 
  

  

  