﻿EUGNATHIDiE. 
  325 
  

  

  and 
  ectopterygoid 
  teeth 
  smaller, 
  very 
  long 
  and 
  slender, 
  and 
  forming 
  

   a 
  dense 
  cluster 
  throughout 
  the 
  length 
  of 
  these 
  elements 
  ; 
  sub- 
  

   operculum 
  of 
  moderate 
  size, 
  about 
  half 
  as 
  large 
  as 
  the 
  nearly 
  

   rectangular 
  operculum. 
  Ossifications 
  in 
  the 
  sheath 
  of 
  the 
  noto- 
  

   chord 
  in 
  the 
  form 
  of 
  distinct 
  hypocentra 
  and 
  pleurocentra. 
  Fulcra 
  

   present 
  on 
  all 
  the 
  fins 
  ; 
  distal 
  articulations 
  of 
  fin-rays 
  very 
  close. 
  

   Pectoral 
  much 
  exceeding 
  the 
  pelvic 
  fins 
  in 
  size, 
  but 
  the 
  latter 
  large 
  ; 
  

   dorsal 
  and 
  anal 
  fins 
  triangular 
  in 
  shape, 
  the 
  former 
  opposite 
  the 
  

   pelvic 
  fins, 
  the 
  latter 
  immediately 
  behind 
  it 
  ; 
  caudal 
  fin 
  forked. 
  

   Scales 
  thin, 
  moderately 
  overlapping, 
  and 
  with 
  a 
  large 
  peg-and- 
  

   socket 
  articulation 
  ; 
  their 
  exposed 
  face 
  ornamented 
  with 
  tubercula- 
  

   tions 
  and 
  striae 
  ; 
  principal 
  flank-scales 
  about 
  as 
  deep 
  as 
  broad, 
  

   several 
  on 
  the 
  ventral 
  aspect 
  much 
  broader 
  than 
  deep. 
  Lateral 
  

   lines 
  inconspicuous. 
  

  

  Osteorachis 
  macrocephahis, 
  Egerton. 
  

  

  (?) 
  1839-44. 
  Pachycormus 
  ? 
  macrurus, 
  L. 
  Agassiz, 
  Poiss. 
  Foss. 
  vol. 
  ii. 
  

  

  pt. 
  ii. 
  p. 
  113, 
  pLlviii. 
  a, 
  fig. 
  3. 
  [Imperfect 
  tail 
  ; 
  Oxford 
  Museum.] 
  

   1868. 
  Osteorachis 
  macrocephahis, 
  Sir 
  P. 
  Egerton, 
  Quart. 
  Journ. 
  Geol. 
  

  

  Soc. 
  vol. 
  xxiv. 
  p. 
  500. 
  

   1872. 
  Osteorachis 
  macrocephahis, 
  Sir 
  P. 
  Egerton, 
  Figs. 
  & 
  Descript. 
  

  

  Brit. 
  Organic 
  Remains, 
  dec. 
  xiii. 
  (Mem. 
  Geol. 
  Surv.), 
  no. 
  5, 
  pi. 
  v. 
  

   1876. 
  Harpactira 
  (Harpactes) 
  velox, 
  Sir 
  P. 
  Egerton, 
  Geol. 
  Mag. 
  [2] 
  

  

  vol. 
  iii. 
  pp. 
  441, 
  576. 
  [Fish 
  ; 
  British 
  Museum.] 
  

   1885. 
  Heterolepidotus 
  grandis, 
  J. 
  W. 
  Davis, 
  Journ. 
  Linn. 
  Soc, 
  Zool. 
  

  

  vol. 
  xviii. 
  p. 
  293, 
  pi. 
  vii. 
  [Fish; 
  J. 
  W. 
  Davis 
  Collection, 
  

  

  Halifax.] 
  

   1890. 
  Harpactira 
  velox, 
  Woodward 
  & 
  Sherborn, 
  Catal. 
  Brit. 
  Foss. 
  

  

  Vertebrata, 
  p. 
  92. 
  

   1890. 
  Osteorhachis 
  macrocephala, 
  Woodward 
  & 
  Sherborn, 
  ibid. 
  p. 
  136. 
  

   1890. 
  Platysiagum 
  grandis, 
  Woodward 
  & 
  Sherborn, 
  ibid. 
  p. 
  151. 
  

   1895. 
  Osteorachis 
  macrocephalus, 
  A. 
  S. 
  Woodward, 
  Geol. 
  Mag. 
  [4] 
  

  

  vol. 
  ii. 
  p. 
  204, 
  pi. 
  vii. 
  fig. 
  10. 
  

  

  Type. 
  Imperfect 
  head 
  and 
  abdominal 
  region 
  ; 
  British 
  Museum. 
  

  

  The 
  type 
  species, 
  attaining 
  a 
  length 
  of 
  about 
  1 
  metre. 
  Form 
  

   and 
  proportions 
  imperfectly 
  known, 
  but 
  the 
  length 
  of 
  the 
  head 
  with 
  

   opercular 
  apparatus 
  probably 
  contained 
  about 
  four 
  times, 
  and 
  the 
  

   maximum 
  depth 
  of 
  the 
  trunk 
  seven 
  times 
  in 
  the 
  total 
  length 
  of 
  the 
  

   fish. 
  Most 
  of 
  the 
  external 
  bones 
  ornamented 
  with 
  a 
  very 
  fine 
  and 
  

   close 
  granulation 
  ; 
  jaws 
  smooth. 
  Operculum 
  considerably 
  deeper 
  

   than 
  broad. 
  The 
  suboperculum 
  is 
  more 
  than 
  twice 
  as 
  broad 
  as 
  

   deep 
  in 
  specimen 
  no. 
  P. 
  3648, 
  and 
  the 
  gular 
  plate 
  in 
  the 
  same 
  

   individual 
  is 
  about 
  two-thirds 
  as 
  broad 
  as 
  long. 
  Dorsal 
  fin 
  with 
  

   not 
  less 
  than 
  18 
  rays, 
  arising 
  in 
  advance 
  of 
  the 
  middle 
  point 
  of 
  the 
  

  

  