﻿CHONDKOSTEID^. 
  35 
  

  

  Type. 
  Various 
  bones 
  ; 
  British 
  Museum. 
  

  

  The 
  type 
  species, 
  of 
  large 
  size, 
  probably 
  attaining 
  a 
  length 
  of 
  not 
  

   less 
  than 
  six 
  or 
  seven 
  metres. 
  Most 
  of 
  the 
  external 
  head-bones 
  

   apparently 
  ornamented 
  with 
  large, 
  well-spaced 
  tubercles, 
  those 
  on 
  

   the 
  suboperculum 
  (?) 
  tending 
  to 
  an 
  arrangement 
  in 
  radiating 
  lines. 
  

   Maxilla 
  smooth, 
  its 
  length 
  somewhat 
  more 
  than 
  twice 
  as 
  great 
  as 
  

   its 
  maximum 
  depth 
  at 
  the 
  anterior 
  expansion 
  ; 
  the 
  supposed 
  sub- 
  

   operculum 
  as 
  broad 
  as 
  deep, 
  with 
  excavated 
  anterior 
  border. 
  

   Caudal 
  fulcral 
  scales 
  smooth, 
  or 
  only 
  in 
  part 
  faintly 
  rugose. 
  

  

  Form. 
  Sf 
  Loc. 
  Upper 
  Lias 
  : 
  Yorkshire. 
  

  

  The 
  following 
  specimens 
  were 
  all 
  obtained 
  from 
  the 
  cliffs 
  in 
  the 
  

   neighbourhood 
  of 
  Whitby. 
  

  

  36185. 
  A 
  large 
  slab 
  displaying 
  numerous 
  bones, 
  among 
  which 
  may 
  

   be 
  recognized 
  the 
  hyomandibular, 
  ceratohyal, 
  supposed 
  

   suboperculum, 
  clavicle, 
  supraclavicle, 
  fragments 
  of 
  squa- 
  

   mous 
  tuberculated 
  bone, 
  and 
  portions 
  of 
  fin-rays. 
  The 
  

   bone 
  interpreted 
  as 
  suboperculum 
  closely 
  resembles 
  that 
  

   element 
  in 
  Chondrosteus, 
  but 
  is 
  not 
  coated 
  with 
  ganoine, 
  

   being 
  covered 
  with 
  coarse 
  tuberculations, 
  of 
  which 
  a 
  few 
  

   are 
  arranged 
  along 
  the 
  radiating 
  lines 
  of 
  growth. 
  

  

  Purchased, 
  1861. 
  

  

  P. 
  3356 
  d-f. 
  Three 
  small 
  slabs 
  exhibiting 
  various 
  bones 
  in 
  a 
  more 
  

   or 
  less 
  fragmentary 
  state. 
  The 
  left 
  clavicle, 
  probably 
  

   belonging 
  to 
  the 
  first 
  slab, 
  is 
  shown 
  from 
  the 
  outer 
  aspect, 
  

   of 
  one-sixth 
  the 
  natural 
  size, 
  in 
  fig. 
  14 
  (p. 
  40), 
  and 
  is 
  

   described 
  and 
  figured 
  by 
  the 
  present 
  writer 
  in 
  Proc. 
  Geol. 
  

   Assoc, 
  vol. 
  xi. 
  pp. 
  34, 
  35, 
  fig. 
  4. 
  The 
  second 
  slab 
  in- 
  

   cludes 
  part 
  of 
  a 
  spatulate 
  bone, 
  with 
  remains 
  of 
  an 
  

   external 
  tubercular 
  ornament. 
  The 
  third 
  slab 
  exhibits 
  

   the 
  bones 
  in 
  a 
  remarkably 
  friable 
  and 
  crushed 
  condition, 
  

   partly 
  pyritised, 
  and 
  comprises 
  both 
  supraclavicles, 
  some 
  

   fin-rays, 
  and 
  part 
  of 
  a 
  hyomandibular. 
  

  

  EnnisTcillen 
  Coll. 
  

  

  P. 
  2262 
  a, 
  b. 
  Two 
  examples 
  of 
  the 
  parasphenoid 
  bone, 
  the 
  first 
  most 
  

   nearly 
  complete 
  and 
  shown 
  of 
  one-quarter 
  the 
  natural 
  

   size, 
  from 
  the 
  inferior 
  aspect, 
  in 
  fig. 
  7. 
  The 
  general 
  form 
  

   of 
  the 
  element 
  is 
  much 
  like 
  that 
  of 
  the 
  modern 
  Acipenser 
  

   (fig. 
  8), 
  but 
  the 
  expansion 
  at 
  the 
  origin 
  of 
  the 
  basiptery- 
  

   goid 
  processes 
  is 
  wider. 
  Egerton 
  Coll. 
  

  

  d2 
  

  

  