﻿322 
  ACTINOPTERYGII. 
  

  

  P. 
  3693. 
  A 
  vertically 
  crushed 
  fish, 
  probably 
  of 
  this 
  species, 
  ex- 
  

   hibiting 
  the 
  small 
  teeth 
  in 
  the 
  maxilla 
  ; 
  Lyme 
  Regis. 
  

  

  Enniskillen 
  Coll. 
  

  

  Ptycholepis 
  monilifer, 
  sp. 
  nov. 
  

   [Plate 
  X. 
  figs. 
  2-4.] 
  

  

  Type. 
  Portions 
  of 
  fish 
  ; 
  British 
  Museum, 
  

  

  The 
  largest 
  known 
  species, 
  probably 
  attaining 
  a 
  length 
  of 
  not 
  less 
  

   than 
  0*6. 
  The 
  ridged 
  ornament 
  of 
  the 
  head 
  fine 
  and 
  closely 
  

   arranged, 
  vermiculating, 
  the 
  ridges 
  often 
  interrupted 
  and 
  in 
  part 
  

   passing 
  into 
  tubercles. 
  The 
  stouter 
  fin-rays 
  ornamented 
  with 
  few 
  

   oblique 
  ridges 
  of 
  ganoine. 
  Scales 
  marked 
  with 
  numerous 
  sharp, 
  

   delicate 
  ridges, 
  sometimes 
  branching, 
  sometimes 
  intercalated, 
  the 
  

   majority 
  directed 
  obliquely 
  downwards 
  and 
  backwards 
  and 
  termi- 
  

   nating 
  in 
  the 
  serrations 
  of 
  the 
  hinder 
  border 
  ; 
  the 
  ridges 
  in 
  all 
  the 
  

   scales, 
  except 
  those 
  of 
  the 
  caudal 
  pedicle, 
  passing 
  forwards 
  into 
  a 
  

   small 
  sparsely 
  tuberculated 
  area 
  at 
  the 
  anterior 
  margin. 
  

  

  Form. 
  Sf 
  Loc. 
  Lower 
  Lias 
  : 
  Dorsetshire. 
  

  

  39868. 
  Type 
  specimen, 
  comprising 
  the 
  right 
  mandibular 
  ramus, 
  

   part 
  of 
  the 
  branchiostegal 
  apparatus, 
  the 
  dorsal 
  and 
  

   caudal 
  fins, 
  numerous 
  scales, 
  and 
  other 
  fragments 
  ; 
  Lyme 
  

   Regis. 
  The 
  right 
  mandibular 
  ramus 
  is 
  shown 
  of 
  the 
  

   natural 
  size 
  in 
  PI. 
  X. 
  fig. 
  2, 
  but 
  is 
  imperfect 
  posteriorly. 
  

   A 
  few 
  small 
  robust 
  conical 
  teeth 
  in 
  single 
  series 
  occur 
  

   sparsely 
  arranged 
  at 
  irregular 
  intervals 
  within 
  the 
  

   alveolar 
  border, 
  which 
  exhibits 
  a 
  slightly 
  sigmoidal 
  

   curvature. 
  The 
  anterior 
  extremity 
  of 
  the 
  ramus 
  is 
  stout, 
  

   though 
  tapering 
  to 
  a 
  blunt 
  point 
  ; 
  and 
  this 
  part 
  is 
  much 
  

   more 
  coarsely 
  ridged 
  than 
  the 
  remainder 
  of 
  the 
  external 
  

   surface. 
  The 
  superficial 
  ridges 
  are 
  very 
  irregular, 
  

   frequently 
  interrupted, 
  branching, 
  or 
  intercalated, 
  having 
  

   a 
  generally 
  backward 
  and 
  downward 
  direction 
  ; 
  and 
  for 
  

   a 
  considerable 
  space 
  bordering 
  the 
  alveolar 
  margin 
  they 
  

   are 
  replaced 
  by 
  fine 
  tubercles. 
  Part 
  of 
  the 
  course 
  of 
  a 
  

   sensory 
  canal 
  is 
  conspicuous 
  postero-inferiorly 
  ; 
  and 
  a 
  

   branch 
  seems 
  to 
  extend 
  from 
  this 
  upwards 
  and 
  forwards 
  

   to 
  the 
  anterior 
  extremity 
  of 
  the 
  bone. 
  The 
  remains 
  of 
  

   the 
  opercular 
  bones 
  are 
  very 
  fragmentary, 
  but 
  one 
  highly- 
  

   ornamented 
  plate 
  is 
  evidently 
  the 
  suboperculum, 
  and 
  this 
  

   is 
  accidentally 
  overlain 
  by 
  the 
  large 
  gular, 
  which 
  is 
  quite 
  

   smooth 
  except 
  in 
  a 
  small 
  mesial 
  tuberculated 
  area 
  ; 
  but 
  

   several 
  of 
  the 
  long 
  and 
  narrow 
  branchiostegal 
  rays 
  are 
  

  

  