﻿174 
  ACTIN0PTER1GII. 
  

  

  consisting 
  of 
  distally 
  bifurcating 
  rays, 
  all 
  with 
  large 
  A-shaped 
  

   fulcra 
  ; 
  pectoral 
  fins 
  much 
  larger 
  than 
  the 
  pelvic 
  pair 
  ; 
  dorsal 
  fin 
  

   arising 
  at 
  the 
  angulation 
  of 
  the 
  back, 
  extending 
  to 
  the 
  caudal 
  

   pedicle, 
  high 
  in 
  front, 
  becoming 
  low 
  behind 
  ; 
  anal 
  fin 
  small 
  ; 
  caudal 
  

   fin 
  forked. 
  Scales 
  covering 
  the 
  whole 
  of 
  the 
  trunk, 
  in 
  regular 
  

   series, 
  united 
  by 
  peg-and-socket 
  articulation, 
  and 
  more 
  or 
  less 
  pec- 
  

   tinated 
  at 
  the 
  hinder 
  border 
  ; 
  the 
  scales 
  of 
  the 
  middle 
  of 
  the 
  flank 
  

   and 
  of 
  the 
  dorsal 
  region 
  much 
  deeper 
  than 
  broad, 
  with 
  more 
  or 
  less 
  

   convex 
  hinder 
  border 
  ; 
  those 
  of 
  the 
  ventral 
  region 
  at 
  least 
  as 
  broad 
  

   as 
  deep 
  ; 
  postclavicular 
  scales 
  very 
  large 
  ; 
  the 
  ridge-scales 
  of 
  the 
  

   caudal 
  pedicle 
  not 
  much 
  enlarged. 
  

  

  Histionotus 
  angularis, 
  Egerton. 
  

  

  1854-55. 
  Histionotus 
  angularis, 
  Sir 
  P. 
  Egerton, 
  Ann. 
  Mag. 
  Nat. 
  Hist, 
  

   [2] 
  vol. 
  xiii. 
  p. 
  434, 
  and 
  Figs. 
  & 
  Descript. 
  Brit. 
  Organic 
  Remains 
  

   (Mem. 
  Geol. 
  Surv.), 
  dec. 
  viii. 
  no. 
  5, 
  pi. 
  v. 
  

  

  1889. 
  Histionotus 
  angularis, 
  J. 
  C. 
  Mansel-Pleydell, 
  Geol. 
  Mag. 
  [3] 
  

   vol. 
  vi. 
  p. 
  241, 
  pi. 
  vii. 
  

  

  Type. 
  Fish, 
  wanting 
  tail 
  ; 
  British 
  Museum. 
  

  

  The 
  type 
  species, 
  attaining 
  a 
  length 
  of 
  about 
  0-2. 
  Length 
  of 
  

   head 
  with 
  opercular 
  apparatus 
  very 
  slightly 
  exceeding 
  its 
  maximum 
  

   depth, 
  and 
  occupying 
  about 
  one-quarter 
  of 
  the 
  total 
  length 
  of 
  the 
  

   fish 
  ; 
  length 
  of 
  the 
  trunk 
  equalling 
  twice 
  its 
  maximum 
  depth, 
  and 
  

   the 
  dorsal 
  angulation 
  measuring 
  approximately 
  148°. 
  The 
  head 
  and 
  

   opercular 
  bones 
  externally 
  ornamented 
  with 
  fine, 
  closely 
  arranged 
  

   rugge 
  ; 
  the 
  large 
  postclavicular 
  plates 
  similarly 
  ornamented. 
  Fin- 
  

   rays 
  stout 
  and 
  smooth 
  ; 
  pectoral 
  fins 
  scarcely 
  twice 
  as 
  large 
  as 
  the 
  

   pelvic 
  pair, 
  and 
  the 
  latter 
  arising 
  in 
  advance 
  of 
  the 
  middle 
  point 
  of 
  

   the 
  trunk 
  ; 
  dorsal 
  fin 
  consisting 
  of 
  at 
  least 
  25 
  rays. 
  Pectinations 
  

   of 
  the 
  scales 
  delicate 
  and 
  confined 
  to 
  their 
  hinder 
  margin, 
  but 
  con- 
  

   spicuous 
  in 
  all 
  regions 
  of 
  the 
  trunk. 
  

  

  Form. 
  Sf 
  Loc. 
  Purbeck 
  Beds 
  : 
  Dorsetshire 
  and 
  "Wiltshire. 
  

  

  P. 
  577. 
  Type 
  specimen, 
  described 
  and 
  figured 
  by 
  Egerton, 
  loc. 
  cit. 
  ;. 
  

   Swanage, 
  Dorsetshire. 
  The 
  impression 
  of 
  the 
  caudal 
  

   region 
  is 
  much 
  less 
  distinct 
  than 
  indicated 
  in 
  the 
  published 
  

   figure, 
  in 
  which 
  the 
  anal 
  fin 
  is 
  erroneously 
  extended. 
  

  

  Egerton 
  Coll. 
  

  

  P. 
  3614. 
  Crushed 
  head 
  and 
  trunk, 
  wanting 
  the 
  greater 
  part 
  of 
  the 
  

   caudal 
  region 
  ; 
  Swanage. 
  EnnisTcillen 
  Coll. 
  

  

  P. 
  5935. 
  Small 
  fish 
  somewhat 
  distorted 
  and 
  with 
  imperfect 
  fins, 
  

   but 
  displaying 
  the 
  bifurcation 
  of 
  the 
  caudal; 
  Swanage, 
  

  

  