﻿PYCNODONTID^]. 
  

  

  233 
  

  

  Genus 
  GYRODUS, 
  Agassiz. 
  

  

  [Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  i. 
  1833, 
  p. 
  16, 
  and 
  pt. 
  ii. 
  1844, 
  p. 
  223.] 
  

  

  Syn. 
  Stromateus, 
  H. 
  D. 
  de 
  Blainville, 
  Nouv. 
  Diet. 
  d'Hist. 
  Nat. 
  vol. 
  xxvii. 
  

   1818, 
  p. 
  333. 
  

  

  Trunk 
  deeply 
  fusiform 
  or 
  discoidal, 
  with 
  a 
  slender 
  abbreviated 
  

   caudal 
  pedicle. 
  Head 
  and 
  opercular 
  bones 
  ornamented 
  with 
  

   tubercles 
  ; 
  cheek 
  and 
  gular 
  region 
  covered 
  with 
  small, 
  imbricating, 
  

   cycloidal 
  scales 
  ; 
  teeth 
  more 
  or 
  less 
  rugose 
  and 
  mammillated, 
  those 
  of 
  

   the 
  vomer 
  in 
  five, 
  and 
  those 
  of 
  the 
  splenial 
  in 
  four 
  regular 
  series. 
  

   Neural 
  and 
  haemal 
  arches 
  of 
  axial 
  skeleton 
  of 
  trunk 
  not 
  expanding 
  

   sufficiently 
  to 
  encircle 
  the 
  notochord. 
  Fin-rays 
  robust, 
  closely 
  

   arranged, 
  articulated 
  and 
  divided 
  distally. 
  Pelvic 
  fins 
  present 
  ; 
  

   dorsal 
  and 
  anal 
  fins 
  low 
  and 
  fringe-like, 
  except 
  in 
  front 
  where 
  they 
  

   rise 
  to 
  an 
  elevated 
  point, 
  these 
  two 
  fins 
  arising 
  at 
  about 
  the 
  same 
  

   point 
  and 
  not 
  extending 
  in 
  advance 
  of 
  the 
  hinder 
  half 
  of 
  the 
  trunk 
  ; 
  

   caudal 
  fin 
  deeply 
  forked, 
  with 
  slender 
  lobes. 
  Scales 
  tuberculated 
  

   or 
  rugose, 
  covering 
  the 
  whole 
  of 
  the 
  trunk. 
  

  

  Gyrodus 
  macrophthalmus, 
  Agassiz. 
  

  

  1833. 
  Microdon 
  abdominalis, 
  L. 
  Agassiz, 
  Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  i. 
  p. 
  16. 
  

   1839^44. 
  Gyrodus 
  macrophthalmus, 
  L. 
  Agassiz, 
  ibid. 
  vol. 
  ii. 
  pt. 
  ii. 
  

  

  pp. 
  224, 
  301, 
  pi. 
  lxvii. 
  

   1839-44. 
  Gyrodus 
  rugosus, 
  L. 
  Agassiz 
  (ex 
  Minister 
  MS.), 
  ibid. 
  p. 
  227, 
  

  

  pi. 
  lxix. 
  [Nearly 
  complete 
  fish 
  ; 
  Pakeontological 
  Museum, 
  

  

  Munich.] 
  

   1842. 
  Gyrodus 
  mceandrinus, 
  G. 
  von 
  Munster, 
  Neues 
  Jahrb. 
  p. 
  45. 
  

  

  [Ditto.] 
  

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

  

  math.-phys. 
  01. 
  vol. 
  vi. 
  p. 
  28. 
  

   1851. 
  Gyrodus 
  rugosus, 
  A. 
  Wagner, 
  ibid. 
  pp. 
  29, 
  45, 
  56. 
  

   1851. 
  Gyrodus 
  mceandrinus, 
  A. 
  Wagner, 
  ibid. 
  p. 
  30. 
  

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

  

  part). 
  

   1862. 
  Gyrodus 
  rugosus, 
  A. 
  Wagner, 
  ibid. 
  vol. 
  ix. 
  p. 
  337. 
  

   1862. 
  Gyrodus 
  dichaotinius, 
  T. 
  C. 
  Winkler, 
  Descript. 
  Poiss. 
  Foss. 
  

  

  Solenhofen 
  (Natuurk. 
  Verhandl. 
  Holland. 
  Maatsch. 
  [2] 
  vol. 
  xiv.), 
  

  

  p. 
  67, 
  fig. 
  12. 
  [Nearly 
  complete 
  fish 
  ; 
  Teyler 
  Museum, 
  Haarlem.] 
  

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

  

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

   1887. 
  Gyrodus 
  macrophthalmus, 
  K. 
  A. 
  von 
  Zittel, 
  Handb. 
  Palseont. 
  

  

  vol. 
  iii. 
  p. 
  239, 
  fig. 
  251. 
  

  

  Type. 
  Nearly 
  complete 
  fish; 
  Palaeontological 
  Museum, 
  Munich. 
  

   The 
  type 
  species, 
  attaining 
  a 
  length 
  of 
  about 
  0*3. 
  Maximum 
  

  

  