﻿236 
  

  

  ACTINOPTERYGII. 
  

  

  1851. 
  Gyrodus 
  frontatus, 
  A. 
  Wagner, 
  Abh. 
  k. 
  bay. 
  Akad. 
  Wiss., 
  math. 
  

  

  phys. 
  01. 
  vol. 
  vi. 
  pp. 
  29, 
  55. 
  

   1851. 
  Gyrodus 
  gracilis 
  = 
  u 
  Microdon 
  hexagonus," 
  A. 
  Wagner, 
  ibid. 
  p. 
  32. 
  

   (?) 
  1852. 
  Gyrodus 
  medius, 
  F. 
  A. 
  Quenstedt, 
  Handb. 
  Petrefakt. 
  p. 
  211, 
  

  

  pi. 
  xvi. 
  fig. 
  2. 
  [Imperfect 
  fish 
  • 
  Tiibingen 
  University 
  Museum.] 
  

   1862. 
  Gyrodus 
  macrophthalmus, 
  A. 
  Wagner, 
  ibid. 
  vol. 
  ix. 
  p. 
  336 
  (in 
  

  

  part). 
  

   1862. 
  Gyrodus 
  gracilis, 
  A. 
  Wagner, 
  ibid. 
  vol. 
  ix. 
  p. 
  338. 
  

   1881. 
  Gyrodus 
  macrophthalmus, 
  B. 
  Vetter, 
  Mittheil. 
  k. 
  mineral.-geol. 
  

  

  Mus. 
  Dresden, 
  pt. 
  iv. 
  p. 
  20 
  (in 
  part). 
  

   1887. 
  Gyrodus 
  frontatus, 
  K. 
  A. 
  von 
  Zittel, 
  Handb. 
  Palseont. 
  vol. 
  iii. 
  

  

  p. 
  242, 
  fig. 
  254. 
  

   1893. 
  Gyrodus 
  frontatus, 
  H. 
  E. 
  Sauvage, 
  Bull. 
  Soc. 
  Hist. 
  Nat. 
  Autun, 
  

  

  vol. 
  vi. 
  p. 
  440. 
  

  

  Type. 
  Nearly 
  complete 
  fish 
  ; 
  British 
  Museum. 
  

  

  A 
  species 
  resembling 
  G. 
  hexagonus 
  in 
  form 
  and 
  proportions, 
  but 
  

   differing 
  in 
  having 
  the 
  tubercular 
  ornament 
  of 
  the 
  scales, 
  without 
  

   reticulations, 
  extending 
  over 
  the 
  ventral 
  half 
  of 
  the 
  fish. 
  

  

  The 
  reticular 
  ornament 
  of 
  the 
  scales 
  in 
  Gyrodus 
  evidently 
  results 
  

   from 
  the 
  connection 
  of 
  scattered 
  tubercles 
  by 
  slight 
  ridges. 
  Such 
  

   a 
  modification 
  may 
  be 
  produced 
  during 
  the 
  growth 
  of 
  the 
  fish, 
  and 
  

   in 
  that 
  case 
  the 
  so-called 
  Gyrodus 
  gracilis 
  is 
  probably 
  the 
  young 
  

   stage 
  of 
  G. 
  macrophthalmus 
  and 
  G. 
  hexagonus 
  as 
  well 
  as 
  that 
  of 
  

   G. 
  frontatus. 
  

  

  Form. 
  <$f 
  Loc. 
  Lower 
  Kimmeridgian 
  (Lithographic 
  Stone) 
  : 
  Bavaria, 
  

   and 
  Ain, 
  France 
  (Sauvage). 
  

  

  P. 
  2096. 
  Type 
  specimen 
  ; 
  Kelheim. 
  Little 
  can 
  be 
  seen 
  of 
  the 
  

   scale- 
  ornament 
  of 
  the 
  ventral 
  half 
  of 
  the 
  fish, 
  but 
  the 
  

   few 
  traces 
  remaining 
  exhibit 
  scattered 
  tubercles 
  without 
  

   reticulation. 
  Egerton 
  Coll. 
  

  

  22515. 
  Remains 
  of 
  a 
  smaller 
  specimen; 
  Solenhofen. 
  

  

  Purchased, 
  1848. 
  

  

  P. 
  3770. 
  Fish 
  originally 
  about 
  0*115 
  in 
  length, 
  wanting 
  the 
  anterior 
  

   half 
  of 
  the 
  head 
  and 
  the 
  caudal 
  fin 
  ; 
  Kelheim. 
  The 
  

   characteristic 
  expansions 
  on 
  the 
  neural 
  and 
  haemal 
  spines 
  

   of 
  the 
  caudal 
  region 
  are 
  conspicuous, 
  as 
  described 
  in 
  the 
  

   next 
  specimen. 
  Six 
  or 
  seven 
  basal 
  cartilages 
  are 
  observed 
  

   in 
  the 
  lobe 
  of 
  the 
  pectoral 
  fin, 
  which 
  is 
  covered 
  with 
  thin 
  

   round 
  scales. 
  Ennishillen 
  Coll. 
  

  

  P. 
  2097. 
  Fine 
  specimen 
  0*075 
  in 
  length, 
  shown 
  of 
  the 
  natural 
  size 
  

   in 
  PI. 
  XYI. 
  fig. 
  2 
  ; 
  Kelheim. 
  The 
  coarse 
  tubercular 
  

   ornament 
  of 
  the 
  cranial 
  roof 
  is 
  shown, 
  while 
  the 
  hinder 
  

   margin 
  of 
  the 
  frontal 
  (fr.) 
  and 
  the 
  boundaries 
  of 
  the 
  

  

  