﻿PHOLIDOPHORID^. 
  449 
  

  

  some 
  specimens. 
  The 
  right 
  and 
  left 
  halves 
  of 
  the 
  rays 
  in 
  the 
  dorsal 
  

   and 
  anal 
  fins 
  are 
  very 
  loosely 
  apposed, 
  and 
  their 
  frequent 
  displace- 
  

   ment 
  in 
  the 
  fossils 
  renders 
  it 
  difficult 
  to 
  count 
  them. 
  

  

  The 
  characters 
  of 
  Pholidophorus 
  are 
  remarkably 
  constant 
  through- 
  

   out 
  the 
  Jurassic 
  period, 
  but 
  most 
  of 
  the 
  later 
  species 
  are 
  more 
  

   elaborately 
  ornamented 
  than 
  those 
  of 
  earlier 
  date. 
  Some 
  of 
  the 
  

   distinctive 
  features 
  of 
  the 
  species 
  described 
  below 
  are 
  enumerated 
  

   in 
  the 
  following 
  synopsis 
  : 
  — 
  

  

  I. 
  Scales 
  not 
  serrated. 
  

  

  Length 
  of 
  head 
  slightly 
  less 
  than 
  maximum 
  

  

  depth 
  of 
  trunk 
  and 
  contained 
  five 
  

  

  times 
  in 
  total 
  length 
  ; 
  dorsal 
  opposite 
  

  

  pelvic 
  fins; 
  scales 
  large 
  and 
  smooth, 
  

  

  scarcely 
  convex 
  border, 
  four 
  deepened 
  

  

  series 
  bechei 
  (p. 
  450). 
  

  

  Stouter, 
  with 
  relatively 
  larger 
  scales 
  .... 
  pachysomus 
  (p. 
  453). 
  

   Smaller, 
  differing 
  in 
  larger 
  size 
  of 
  head 
  

  

  which 
  equals 
  about 
  one 
  quarter 
  of 
  the 
  

  

  total 
  length 
  latiusculus 
  (p. 
  454). 
  

  

  More 
  slender 
  ; 
  head 
  occupying 
  one-fifth 
  ; 
  

  

  dorsal 
  arising 
  behind 
  pelvic 
  fins 
  ; 
  

  

  scales 
  thinner, 
  with 
  convex 
  hinder 
  

  

  border 
  stricklandi 
  (p. 
  456). 
  

  

  Somewhat 
  stouter 
  and 
  head 
  smaller; 
  

  

  dorsal 
  opposite 
  pelvic 
  fins 
  ; 
  scales 
  very 
  

  

  thin, 
  none 
  much 
  deeper 
  than 
  broad 
  . 
  . 
  caudalis 
  (p. 
  457). 
  

   Head 
  occupying 
  one-fifth; 
  dorsal 
  opposed 
  

  

  to 
  pelvic 
  fins 
  ; 
  scales 
  coarsely 
  but 
  

  

  feebly 
  rugose, 
  and 
  about 
  six 
  series 
  

  

  deepened 
  germanicus 
  (p. 
  459). 
  

  

  Head 
  occupying 
  one-fourth 
  ; 
  dorsal 
  arising 
  

  

  behind 
  pelvic 
  fins 
  ; 
  fulcra 
  remarkably 
  

  

  large 
  ; 
  scales 
  smooth, 
  four 
  series 
  much 
  

  

  deepened, 
  especially 
  that 
  of 
  lateral 
  

  

  line 
  purbeckensis 
  (p. 
  460). 
  

  

  II. 
  Scales 
  serrated. 
  

  

  Head 
  occupying 
  one-fourth 
  ; 
  dorsal 
  opposed 
  

  

  to 
  pelvic 
  fins 
  ; 
  sparse 
  denticulations 
  

  

  on 
  the 
  four 
  deepened 
  flank-series 
  of 
  

  

  scales 
  : 
  . 
  . 
  higginsi 
  (p. 
  461). 
  

  

  Very 
  slender, 
  and 
  head 
  occupying 
  one-fifth 
  ; 
  

  

  dorsal 
  arising 
  behind 
  pelvic 
  fins 
  ; 
  

  

  scales 
  scarcely 
  deepened, 
  partly 
  ridged 
  

  

  along 
  lines 
  of 
  growth, 
  and 
  serrations 
  

  

  coarse 
  crenulatus 
  (p. 
  463), 
  

  

  Stouter, 
  with 
  larger 
  head 
  ; 
  scales 
  smooth 
  

  

  and 
  more 
  finely 
  serrated, 
  five 
  series 
  

  

  deepened 
  on 
  flank 
  , 
  Umbatns 
  (p. 
  464). 
  

  

  PART 
  III. 
  2 
  Gt 
  

  

  