﻿134 
  ACTINOPTEKYUII. 
  

  

  1854. 
  JEchmodus 
  conjluens, 
  leiosomus, 
  speciosus, 
  J. 
  Morris, 
  ibid. 
  pp. 
  316, 
  

  

  317. 
  

   1869. 
  JEchmodus 
  orbicularis, 
  J. 
  Morris, 
  Geol. 
  Mag. 
  vol. 
  vi. 
  p. 
  337, 
  pl.x. 
  

  

  [Nearly 
  complete 
  fish 
  ; 
  W. 
  H. 
  Huddleston 
  Coll.] 
  

   1890. 
  Dapedius 
  leiosomus, 
  orbicularis, 
  politus, 
  Woodward 
  & 
  Sherborn, 
  

  

  Catal. 
  Brit. 
  Foss. 
  Vertebrata, 
  pp. 
  58, 
  59. 
  

  

  Type, 
  Imperfect 
  fish. 
  

  

  The 
  type 
  species, 
  attaining 
  a 
  length 
  of 
  about 
  0*4. 
  Maximum 
  

   depth 
  of 
  trunk 
  about 
  equal 
  to 
  its 
  length 
  (exclusive 
  of 
  the 
  caudal 
  

   fin) 
  and 
  four 
  times 
  as 
  great 
  as 
  the 
  depth 
  of 
  the 
  caudal 
  pedicle. 
  

   Head 
  with 
  opercular 
  apparatus 
  occupying 
  about 
  one-quarter 
  of 
  the 
  

   total 
  length; 
  the 
  external 
  bones 
  in 
  the 
  adult 
  ornamented 
  with 
  

   very 
  coarse 
  tuberculations, 
  closely 
  arranged, 
  more 
  or 
  less 
  flattened 
  

   or 
  even 
  hollowed 
  on 
  the 
  operculum, 
  and 
  often 
  fused 
  into 
  shoit 
  

   vermiculating 
  ridges. 
  Marginal 
  teeth 
  robust, 
  partly 
  unicuspid 
  7 
  

   partly 
  bicuspid. 
  Pelvic 
  fins 
  arising 
  midway 
  between 
  the 
  pectorals 
  

   and 
  the 
  anal 
  ; 
  dorsal 
  fin 
  with 
  30, 
  and 
  anal 
  fin 
  with 
  18 
  rays. 
  Scales 
  

   nearly 
  smooth, 
  with 
  few 
  minute 
  transverse 
  striae 
  and 
  sparse 
  puncta- 
  

   tions 
  ; 
  the 
  hinder 
  border 
  delicately 
  serrated. 
  

  

  The 
  small 
  specimens 
  named 
  Dapedius 
  leiosomus 
  differ 
  from 
  the 
  

   typical 
  D. 
  politus 
  in 
  their 
  somewhat 
  more 
  elongated 
  form 
  and 
  in 
  

   the 
  sparseness 
  of 
  their 
  tubercular 
  ornament 
  ; 
  but 
  they 
  are 
  proved 
  

   to 
  be 
  immature 
  by 
  the 
  non-fusion 
  of 
  the 
  parietal, 
  frontal, 
  and 
  

   squamosal 
  bones. 
  The 
  Collection 
  seems 
  to 
  exhibit 
  every 
  gradation 
  

   between 
  these 
  fishes 
  and 
  the 
  large 
  specimens 
  commonly 
  named 
  

   Tetragonolepis 
  conjluens. 
  

  

  Form. 
  Sf 
  Loc. 
  Lower 
  Lias 
  : 
  Dorsetshire. 
  

  

  All 
  the 
  following 
  specimens 
  were 
  obtained 
  from 
  the 
  Lower 
  Lias 
  

   of 
  Lyme 
  Eegis, 
  Dorsetshire 
  : 
  — 
  

  

  P. 
  3555. 
  Head 
  of 
  large 
  individual, 
  with 
  pectoral 
  fin 
  and 
  anterior 
  

   abdominal 
  scales 
  ; 
  the 
  type 
  specimen 
  of 
  the 
  so-called 
  

   Tetragonolepis 
  confiuens 
  described 
  and 
  figured 
  by 
  Agassiz 
  y 
  

   loc. 
  cit. 
  EnnisJcillen 
  Coll. 
  

  

  P. 
  3550 
  a. 
  Eemains 
  of 
  head 
  and 
  abdominal 
  region 
  of 
  a 
  similar 
  fish. 
  

  

  Enniskillen 
  Coll. 
  

  

  P. 
  3556. 
  Imperfect 
  fish 
  0-39 
  in 
  length, 
  with 
  displaced 
  facial 
  bones 
  

   and 
  wanting 
  the 
  anal 
  fin. 
  The 
  ornament 
  upon 
  the 
  oper- 
  

   cular 
  and 
  facial 
  bones 
  is 
  relatively 
  as 
  coarse 
  as 
  in 
  the 
  

   preceding 
  specimen, 
  but 
  there 
  is 
  less 
  tendency 
  towards 
  the 
  

   fusion 
  of 
  the 
  tubercles. 
  The 
  tuberculations 
  upon 
  the 
  dorsal 
  

   ridge-scales 
  and 
  the 
  adjoining 
  series 
  are 
  to 
  a 
  considerable 
  

   extent 
  fused 
  into 
  longitudinal 
  rugae. 
  Enniskillen 
  Coll. 
  

  

  