﻿OLIGOPLETJRID-E. 
  499 
  

  

  spines 
  in 
  advance 
  of 
  the 
  dorsal 
  fin, 
  and 
  part 
  of 
  the 
  rays 
  

   apparently 
  of 
  the 
  pectoral 
  fin. 
  The 
  second 
  specimen 
  dis- 
  

   plays 
  the 
  considerable 
  expansion 
  of 
  the 
  laminae 
  of 
  the 
  

   neural 
  and 
  haemal 
  arches, 
  the 
  acuminate 
  anterior 
  portion 
  

   of 
  the 
  dorsal 
  fin 
  with 
  fulcra 
  on 
  the 
  first 
  ray, 
  and 
  the 
  

   rounded 
  form 
  of 
  the 
  scales. 
  Lewis 
  Coll. 
  

  

  P. 
  5994. 
  Imperfect 
  head 
  and 
  anterior 
  abdominal 
  region 
  with 
  pec- 
  

   toral 
  fin, 
  apparently 
  of 
  this 
  fish 
  ; 
  Hakel. 
  The 
  head 
  is 
  

   too 
  fragmentary 
  for 
  description 
  and 
  the 
  vertebral 
  centra 
  

   are 
  obscure. 
  The 
  pectoral 
  fin-rays 
  are 
  broad, 
  much 
  

   divided 
  and 
  very 
  closely 
  articulated 
  in 
  the 
  distal 
  portion 
  ; 
  

   fulcra 
  occur 
  on 
  the 
  anterior 
  margin 
  of 
  the 
  fin, 
  and 
  there 
  

   are 
  traces 
  of 
  slender 
  basal 
  bones. 
  Lewis 
  Coll. 
  

  

  It 
  is 
  still 
  not 
  possible 
  to 
  distinguish 
  from 
  Spathiurus 
  the 
  genus 
  

   Opsigonus 
  (D. 
  G. 
  Kramberger, 
  in 
  F. 
  Bassani, 
  Denkschr. 
  k. 
  Akad. 
  

   Wiss., 
  math.-naturw. 
  CI. 
  vol. 
  xlv. 
  1882, 
  p. 
  200), 
  from 
  the 
  Cretaceous 
  

   of 
  the 
  Island 
  of 
  Lesina, 
  Dalmatia. 
  It 
  is 
  not 
  determined, 
  however, 
  

   whether 
  this 
  fish 
  had 
  a 
  rounded 
  or 
  forked 
  tail, 
  whether 
  fulcra 
  are 
  

   present 
  or 
  absent 
  on 
  any 
  fin 
  except 
  the 
  caudal, 
  and 
  whether 
  or 
  not 
  

   there 
  is 
  a 
  series 
  of 
  free 
  neural 
  spines 
  in 
  the 
  abdominal 
  region. 
  

   The 
  single 
  known 
  species 
  is 
  Opsigonus 
  megaluriformis 
  (Kramberger, 
  

   loc. 
  cit. 
  p. 
  200, 
  and 
  Rad. 
  Jugoslav. 
  Akad. 
  vol. 
  lxxii. 
  1885, 
  p. 
  14, 
  

   pi. 
  iv. 
  fig. 
  1, 
  and 
  Soc. 
  Hist.-Nat. 
  Croatica, 
  vol. 
  i. 
  1886, 
  p. 
  125), 
  the 
  

   type 
  specimen 
  being 
  preserved 
  in 
  the 
  Geological 
  Museum 
  of 
  the 
  

   University 
  of 
  Agram. 
  The 
  name 
  of 
  Opsigonus 
  gracilis 
  is 
  given 
  by 
  

   J. 
  Y. 
  Eohon 
  (Mem. 
  Acad. 
  Imp. 
  Sci. 
  St. 
  Petersbourg, 
  [7] 
  vol. 
  xxxviii. 
  

   no. 
  1, 
  1890, 
  p. 
  11, 
  pi. 
  i. 
  fig. 
  6) 
  to 
  a 
  small 
  Palseoniscid 
  fish 
  from 
  the 
  

   Jurassic 
  of 
  Ust-Balei, 
  Government 
  of 
  Irkutsk, 
  Siberia, 
  now 
  in 
  the 
  

   Museum 
  of 
  the 
  Imperial 
  Academy 
  of 
  Sciences, 
  St. 
  Petersburg. 
  

  

  The 
  following 
  specimens 
  probably 
  represent 
  a 
  member 
  of 
  the 
  

   family 
  Oligopleuridae, 
  but 
  are 
  too 
  imperfect 
  for 
  precise 
  determina- 
  

   tion 
  : 
  — 
  

  

  P. 
  7584. 
  Fragment 
  of 
  trunk 
  and 
  fin 
  labelled 
  " 
  Calamoporus 
  

   cylindricus, 
  Agass.," 
  by 
  Agassiz, 
  evidently 
  intended 
  for 
  

   Calamopleurus 
  cylinclricus, 
  L. 
  Agassiz, 
  Edinb. 
  New 
  Phil. 
  

   Journ. 
  vol. 
  xxx. 
  (1841), 
  p. 
  84, 
  and 
  Comptes 
  Rendus, 
  

   vol. 
  xviii. 
  (1844), 
  p. 
  1012 
  ; 
  Cretaceous, 
  Province 
  of 
  Ceara, 
  

   Brazil. 
  The 
  scales 
  are 
  cycloidal, 
  very 
  much 
  imbricating 
  

   and 
  apparently 
  longer 
  than 
  deep 
  ; 
  the 
  fin-rays 
  are 
  widely 
  

   spaced 
  and 
  much 
  divided 
  distally. 
  History 
  unknown. 
  

  

  2k2 
  

  

  