﻿PTCNODONTID^!. 
  189 
  

  

  in 
  the 
  more 
  arched 
  form 
  of 
  the 
  back, 
  deeper 
  trunk, 
  and 
  the 
  

   remarkable 
  development 
  of 
  the 
  pectoral, 
  dorsal, 
  and 
  anal 
  fins. 
  

  

  Form. 
  Sf 
  Log. 
  Lower 
  Kimmeridgian 
  (Lithographic 
  Stone) 
  : 
  Ba- 
  

   varia. 
  

  

  Not 
  represented 
  in 
  the 
  Collection. 
  

  

  A 
  fish 
  from 
  the 
  Lithographic 
  Stone 
  of 
  Cirin, 
  Ain, 
  France, 
  much 
  

   resembling 
  the 
  two 
  preceding 
  species, 
  is 
  named 
  N. 
  margaritee, 
  

   Thiolliere 
  (Bull. 
  Soc. 
  Geol. 
  Prance, 
  [2] 
  vol. 
  xv. 
  1858, 
  p. 
  783), 
  and 
  

   figured 
  without 
  description 
  in 
  Thiolliere, 
  Poiss. 
  Foss. 
  Bugey, 
  pt. 
  ii. 
  

   (1873), 
  pi. 
  vi. 
  fig. 
  4. 
  

  

  Either 
  to 
  the 
  Macrosemiidge 
  or 
  to 
  the 
  Semionotidae 
  may 
  also 
  per- 
  

   haps 
  be 
  referred 
  the 
  problematical 
  Triassic 
  genus 
  Oriliurus 
  (R. 
  Kner, 
  

   Sitzungsb. 
  k. 
  Akad. 
  Wiss., 
  math.-naturw. 
  CI. 
  vol. 
  liii. 
  1866, 
  p. 
  163). 
  

   The 
  trunk 
  is 
  comparatively 
  elongated 
  and 
  is 
  almost 
  or 
  quite 
  scale- 
  

   less 
  on 
  the 
  flanks. 
  A 
  few 
  of 
  the 
  inner 
  teeth 
  are 
  enlarged 
  and 
  

   tritoral. 
  There 
  is 
  little 
  or 
  no 
  ossification 
  in 
  the 
  notochordal 
  sheath, 
  

   and 
  the 
  ribs 
  are 
  extremely 
  delicate. 
  The 
  pectoral 
  fins 
  are 
  large 
  

   and 
  the 
  pelvic 
  fins 
  remote 
  ; 
  the 
  dorsal 
  fin 
  has 
  an 
  extended 
  base-line 
  

   but 
  is 
  not 
  acuminate, 
  and 
  the 
  anal 
  is 
  relatively 
  very 
  small 
  ; 
  the 
  

   caudal 
  fin 
  is 
  truncated, 
  not 
  forked. 
  A 
  few 
  undivided 
  and 
  unarti- 
  

   culated 
  rays 
  occur 
  at 
  the 
  origin 
  of 
  the 
  dorsal 
  and 
  caudal 
  fins, 
  but 
  

   ordinary 
  fulcra 
  are 
  absent. 
  All 
  the 
  fin-rays 
  are 
  delicate, 
  and 
  those 
  

   of 
  the 
  dorsal 
  and 
  anal 
  fins, 
  though 
  articulated, 
  are 
  not 
  branched 
  

   more 
  than 
  once. 
  An 
  elongated 
  large 
  scale 
  occurs 
  in 
  front 
  of 
  the 
  

   anal 
  fin. 
  The 
  type 
  species, 
  0. 
  sturi 
  (Kner, 
  loc. 
  cit. 
  p. 
  163, 
  pi. 
  ii. 
  

   fig. 
  1), 
  is 
  founded 
  on 
  a 
  unique 
  specimen 
  from 
  the 
  Keuper 
  of 
  Raibl, 
  

   Carinthia, 
  in 
  the 
  Museum 
  of 
  the 
  Austrian 
  Geological 
  Survey, 
  

   Vienna. 
  Another 
  form 
  from 
  the 
  " 
  Hauptdolomit 
  " 
  of 
  Lumezzane, 
  

   Lombardy, 
  is 
  also 
  described 
  by 
  W. 
  Deecke, 
  Palseontogr. 
  vol. 
  xxxv. 
  

   (1889), 
  p. 
  136, 
  pi. 
  vii. 
  fig. 
  9. 
  

  

  Family 
  PYCNODONTIDiE. 
  

  

  Trunk 
  deeply 
  fusiform 
  or 
  cycloidal. 
  Cranial 
  bones 
  robust, 
  and 
  

   a 
  median 
  occipital 
  plate 
  separating 
  the 
  parietal 
  elements 
  ; 
  facial 
  

   bones 
  delicate 
  or 
  wanting 
  ; 
  opercular 
  apparatus 
  reduced 
  to 
  a 
  small 
  

   operculum, 
  large 
  preoperculum, 
  and 
  not 
  more 
  than 
  two 
  branchio- 
  

   stegal 
  rays 
  ; 
  mandibular 
  suspensorium 
  much 
  inclined 
  forwards 
  and 
  

   gape 
  of 
  mouth 
  small 
  ; 
  teeth 
  prehensile 
  on 
  the 
  premaxilla 
  and 
  dentary, 
  

   wanting 
  on 
  the 
  maxilla 
  (if 
  this 
  bone 
  be 
  present) 
  and 
  the 
  pterygo- 
  

   palatine 
  arcade, 
  tritoral 
  on 
  the 
  single 
  vomer 
  and 
  the 
  splenials 
  ; 
  all 
  

  

  