﻿290 
  ACTriSOPTEKYGII. 
  

  

  there 
  is 
  a 
  large 
  gular 
  plate 
  covering 
  the 
  whole 
  of 
  the 
  space 
  between 
  

   the 
  mandibular 
  rami 
  in 
  front 
  of 
  them. 
  

  

  The 
  notochord 
  is 
  persistent, 
  but 
  there 
  are 
  usually 
  some 
  traces 
  

   of 
  hypocentra 
  and 
  pleurocentra, 
  and 
  these 
  are 
  often 
  robust 
  in 
  the 
  

   larger 
  individuals. 
  In 
  the 
  abdominal 
  region 
  there 
  are 
  slender 
  ribs 
  

   loosely 
  articulated 
  with 
  short 
  prominences 
  on 
  the 
  hypocentra 
  ; 
  and 
  

   there 
  is 
  the 
  series 
  of 
  large 
  free 
  neural 
  spines, 
  so 
  well 
  known 
  in 
  

   •Caturus, 
  extending 
  as 
  far 
  as 
  the 
  anterior 
  portion 
  of 
  the 
  dorsal 
  fin. 
  

   In 
  the 
  caudal 
  region 
  the 
  neural 
  and 
  haemal 
  arches 
  are 
  stout, 
  and 
  

   the 
  haemal 
  spines 
  at 
  the 
  base 
  of 
  the 
  caudal 
  fin 
  are 
  somewhat 
  

   expanded. 
  

  

  A 
  single 
  pair 
  of 
  transversely 
  extended 
  supratemporal 
  plates 
  over- 
  

   laps 
  the 
  occiput, 
  and 
  immediately 
  behind 
  is 
  observed 
  the 
  exposed 
  

   portion 
  of 
  a 
  pair 
  of 
  large 
  triangular 
  post-temporals, 
  which 
  support 
  

   the 
  pectoral 
  arch. 
  The 
  supraclavicle 
  is 
  long 
  and 
  narrow, 
  and 
  the 
  

   arched 
  clavicle 
  is 
  relatively 
  very 
  large. 
  The 
  latter 
  element 
  is 
  

   contracted 
  and 
  thickened 
  above, 
  with 
  a 
  considerable 
  outer 
  lamina 
  

   mesially, 
  and 
  tapering 
  to 
  a 
  delicate 
  point 
  below 
  where 
  it 
  meets 
  its 
  

   fellow 
  of 
  the 
  opposite 
  side. 
  On 
  its 
  antero- 
  superior 
  angulation 
  there 
  

   are 
  several 
  longitudinal 
  rugae. 
  The 
  scapula, 
  coracoids, 
  and 
  basals 
  

   are 
  not 
  satisfactorily 
  known 
  ; 
  but 
  it 
  is 
  clear 
  that 
  the 
  immediate 
  

   supports 
  of 
  the 
  pectoral 
  fin-rays 
  were 
  much 
  like 
  those 
  of 
  Ophiopsis 
  

   (p. 
  167, 
  PI. 
  III. 
  fig. 
  3), 
  the 
  hindermost 
  basal 
  being 
  the 
  largest. 
  

   The 
  pelvic 
  fin-supports 
  are 
  irregularly 
  hourglass-shaped, 
  much 
  more 
  

   expanded 
  proximally 
  than 
  distally, 
  as 
  shown 
  in 
  Caturus 
  (PI. 
  IX. 
  

   fig. 
  3). 
  Conspicuous 
  biserial 
  fulcra 
  appear 
  on 
  all 
  the 
  fins. 
  

  

  Thick 
  rhombic 
  ganoid 
  scales 
  cover 
  the 
  whole 
  of 
  the 
  trunk, 
  and 
  

   are 
  arranged 
  in 
  regular 
  oblique 
  series 
  except 
  immediately 
  at 
  the 
  

   base 
  of 
  the 
  caudal 
  fin, 
  where 
  the 
  last 
  row 
  is 
  directly 
  related 
  to 
  

   covering 
  the 
  base 
  of 
  the 
  rays. 
  Each 
  scale 
  is 
  strengthened 
  on 
  its 
  

   inner 
  face 
  with 
  a 
  vertical 
  median 
  rib 
  ; 
  and 
  the 
  principal 
  flank-scales 
  

   are 
  also 
  united 
  by 
  a 
  peg-and-socket 
  articulation. 
  A 
  series 
  of 
  four 
  

   large 
  postclavicular 
  scales 
  is 
  connected 
  with 
  the 
  clavicle. 
  None 
  of 
  

   the 
  ordinary 
  scales, 
  however, 
  are 
  enlarged 
  either 
  along 
  the 
  dorsal 
  

   margin 
  or 
  in 
  the 
  region 
  of 
  the 
  anus. 
  The 
  position 
  of 
  the 
  latter 
  

   close 
  to 
  the 
  origin 
  of 
  the 
  anal 
  fin 
  is 
  indicated 
  by 
  coprolitic 
  matter 
  in 
  

   no. 
  48006. 
  Some 
  of 
  the 
  ventral 
  scales 
  in 
  the 
  region 
  of 
  the 
  pectoral 
  

   fins 
  are 
  much 
  subdivided. 
  

  

  