﻿234 
  ACTINOPTERTGII. 
  

  

  depth 
  of 
  trunk 
  not 
  exceeding 
  its 
  length 
  from 
  the 
  scapular 
  arch 
  to 
  the 
  

   base 
  of 
  the 
  caudal 
  fin, 
  and 
  head 
  with 
  opercular 
  apparatus 
  occupying 
  

   one-third 
  of 
  the 
  total 
  length 
  exclusive 
  of 
  the 
  caudal 
  fin. 
  [Dentition 
  

   unsatisfactorily 
  known 
  but] 
  principal 
  teeth 
  exhibiting 
  two 
  crimped 
  

   rings 
  on 
  crown. 
  Dorsal 
  fin 
  occupying 
  the 
  hinder 
  half 
  of 
  the 
  back, 
  

   and 
  its 
  maximum 
  elevation 
  equalling 
  about 
  one-fourth 
  of 
  the 
  depth 
  

   of 
  the 
  trunk 
  at 
  its 
  insertion. 
  Scales 
  towards 
  the 
  dorsal 
  margin 
  

   conspicuously 
  tuberculated, 
  the 
  others 
  marked 
  with 
  a 
  coarse 
  reticu- 
  

   lation. 
  

  

  Form. 
  Sr 
  Loc. 
  Lower 
  Kimmeridgian 
  (Lithographic 
  Stone) 
  : 
  Bavaria. 
  

  

  P. 
  1620, 
  P. 
  3771. 
  Nearly 
  complete 
  fish 
  0*19 
  in 
  length, 
  partly 
  in 
  

   counterpart, 
  wanting 
  the 
  greater 
  part 
  of 
  the 
  dorsal 
  and 
  

   anal 
  fins 
  ; 
  Kelheim. 
  Egerton 
  and 
  EnnisTcillen 
  Colls. 
  

  

  P. 
  3766. 
  Portion 
  of 
  trunk 
  of 
  a 
  large 
  fish, 
  probably 
  of 
  this 
  species 
  ; 
  

   Kelheim. 
  EnnisTcillen 
  Coll. 
  

  

  P. 
  1621. 
  Imperfect 
  anterior 
  portion 
  of 
  small 
  fish, 
  probably 
  of 
  this 
  

   species 
  ; 
  Kelheim. 
  Egerton 
  Coll. 
  

  

  Gyrodus 
  hexagonus 
  (Blainville). 
  

   [Plate 
  XVI. 
  fig. 
  3.] 
  

  

  1818. 
  Stromateus 
  hexagonus, 
  H. 
  D. 
  de 
  Blainville, 
  Nouv. 
  Diet. 
  d'Hist. 
  

  

  Nat. 
  vol. 
  xxvii. 
  p. 
  334. 
  

   1833-44. 
  Microdon 
  hexagonus, 
  L. 
  Agassiz, 
  Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  i. 
  

  

  p. 
  16, 
  pt. 
  ii. 
  pp. 
  184, 
  206, 
  pi. 
  lxix. 
  c. 
  figs. 
  4, 
  5. 
  

   1833-44. 
  Microdon 
  analis, 
  L. 
  Agassiz, 
  ibid. 
  pt. 
  i. 
  p. 
  16, 
  pt. 
  ii. 
  p. 
  207, 
  

  

  pi. 
  lxix.c. 
  tig. 
  3. 
  [Nearly 
  complete 
  fish 
  ; 
  Palaeontological 
  Museum, 
  

  

  Munich.] 
  

   1844. 
  Gyrodus 
  analis, 
  L. 
  Agassiz, 
  ibid. 
  pt. 
  ii. 
  p. 
  300. 
  

   1851. 
  Gyrodus 
  hexagonus, 
  A. 
  Wagner, 
  Abh. 
  k. 
  bay. 
  Akad. 
  Wiss., 
  

  

  math.-phys. 
  CI. 
  vol. 
  vi. 
  pp. 
  32, 
  40, 
  44, 
  pi. 
  hi. 
  fig. 
  1. 
  

  

  1851. 
  Gyrodus 
  Zepturus, 
  A. 
  Wagner, 
  ibid. 
  vol. 
  vi. 
  pp. 
  31, 
  56. 
  [Imperfect 
  

   fish 
  ; 
  Palaeontological 
  Museum, 
  Munich.] 
  

  

  1852. 
  Gyrodus 
  rugosus, 
  F. 
  A. 
  Quenstedt 
  (errore), 
  Handb. 
  Petrefakt. 
  

   p. 
  211, 
  pi. 
  xvi. 
  fig. 
  1. 
  

  

  1862. 
  Gyrodus 
  hexagonus, 
  A. 
  Wagner, 
  loc. 
  cit. 
  vol. 
  ix. 
  p. 
  334. 
  

  

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

  

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

   1887. 
  Gyrodus 
  hexagonus, 
  K. 
  A. 
  von 
  Zittel, 
  Handb. 
  Paleeont. 
  vol. 
  iii. 
  

  

  p. 
  241, 
  fig. 
  252. 
  

  

  Type. 
  Nearly 
  complete 
  fish 
  and 
  fragment; 
  Palseontologieal 
  

   Museum, 
  Munich, 
  and 
  British 
  Museum. 
  

  

  A 
  species, 
  so 
  far 
  as 
  known, 
  closely 
  similar 
  to 
  the 
  type, 
  only 
  

   differing 
  in 
  the 
  relatively 
  greater 
  protuberance 
  of 
  the 
  abdominal 
  

  

  