﻿280 
  

  

  ACTIN0PTEKYG11. 
  

  

  Caudal 
  pleurocentra 
  and 
  hypocentra 
  

   never 
  annular 
  ; 
  marginal 
  teeth 
  large, 
  

   splenial 
  teeth 
  much 
  smaller 
  and 
  

   mostly 
  in 
  single 
  series 
  ; 
  dorsal 
  fin 
  in 
  

   advance 
  of 
  anal 
  ; 
  caudal 
  fin 
  forked 
  ; 
  

   scales 
  smooth 
  or 
  delicately 
  pectinated, 
  

   deeply 
  overlapping 
  Caturus 
  (p. 
  329). 
  

  

  Ditto, 
  but 
  dorsal 
  fin 
  opposed 
  to 
  anal 
  .... 
  

  

  Caudal 
  pleurocentra 
  and 
  hypocentra 
  in 
  

   form 
  of 
  alternating 
  complete 
  rings; 
  

   dentary 
  teeth 
  large, 
  maxillary 
  and 
  

   splenial 
  teeth 
  much 
  smaller 
  and 
  in 
  

   a 
  single 
  close 
  series; 
  dorsal 
  fin 
  in 
  

   advance 
  of 
  anal 
  ; 
  caudal 
  fin 
  forked 
  ; 
  

   scales 
  deeply 
  overlapping 
  

  

  II. 
  Vertebral 
  ossifications 
  in 
  the 
  form 
  of 
  solid 
  

  

  discs. 
  

   External 
  bones 
  much 
  ornamented 
  and 
  

   cranial 
  roof 
  without 
  elevations 
  ; 
  

   marginal 
  teeth 
  large 
  and 
  regular; 
  

   scales 
  thick, 
  with 
  feeble 
  peg-and- 
  

   socket 
  articulation, 
  not 
  deepened 
  on 
  

   the 
  flank, 
  very 
  narrow 
  ventrally 
  .... 
  

  

  III. 
  Vertebral 
  ossifications 
  uncertain, 
  but 
  pro- 
  

  

  bably 
  rings. 
  

   Much 
  resembling 
  Neorhombolepis, 
  but 
  dif- 
  

   fering 
  especially 
  in 
  the 
  development 
  

   of 
  a 
  pair 
  of 
  elevations 
  on 
  the 
  cranial 
  

   roof 
  immediately 
  behind 
  the 
  eyes 
  . 
  . 
  

  

  Callopterus 
  (p. 
  351). 
  

  

  Eurycormus 
  (p. 
  352). 
  

  

  Neorhombolepis 
  (p. 
  355). 
  

  

  Lophiostomus 
  (p. 
  358). 
  

  

  Genus 
  EUGNATHUS, 
  Agassiz. 
  

  

  [Poiss. 
  Poss. 
  vol. 
  ii. 
  pt. 
  ii. 
  1844, 
  p. 
  97. 
  l 
  ] 
  

  

  Syn. 
  Lissolepis, 
  J. 
  W. 
  Davis, 
  Ann. 
  Mag. 
  Nat. 
  Hist. 
  [5] 
  vol. 
  xiii. 
  1884, 
  

   p. 
  448. 
  

   Isojpholis, 
  K. 
  A. 
  von 
  Zittel, 
  Handb. 
  Palseont. 
  vol. 
  iii. 
  1887, 
  

   p. 
  216. 
  

  

  Trunk 
  elongate-fusiform. 
  External 
  bones 
  feebly 
  ornamented 
  

   with 
  tuberculations 
  or 
  rugae 
  ; 
  teeth 
  relatively 
  large 
  and 
  spaced 
  on 
  

   the 
  dentary, 
  smaller 
  and 
  more 
  closely 
  arranged 
  on 
  the 
  margin 
  of 
  

   the 
  upper 
  jaw, 
  minute 
  and 
  almost 
  granular 
  on 
  the 
  inner 
  bones, 
  in 
  

  

  1 
  The 
  name 
  Eugnathus 
  appears 
  to 
  have 
  been 
  first 
  quoted, 
  but 
  without 
  

   definition, 
  by 
  Sir 
  P. 
  Egerton, 
  London 
  & 
  Edinb. 
  Phil. 
  Mag. 
  [3] 
  vol. 
  viii. 
  1836, 
  

   p. 
  368. 
  

  

  