﻿CHONDBOSTEID^I. 
  33 
  

  

  right 
  side. 
  The 
  right 
  clavicle 
  and 
  infraclavicle 
  are 
  shown, 
  

   of 
  the 
  natural 
  size, 
  in 
  PL 
  I. 
  fig. 
  5. 
  The 
  clavicle 
  (cl.) 
  is 
  

   precisely 
  similar 
  to 
  that 
  of 
  Acipenser 
  (fig. 
  15, 
  p. 
  40) 
  in 
  

   shape, 
  but 
  the 
  infraclavicle 
  (i.cl.) 
  is 
  relatively 
  smaller 
  than 
  

   the 
  corresponding 
  element 
  of 
  the 
  recent 
  genus. 
  

  

  Ennish'dlen 
  Coll. 
  

  

  35056. 
  Trunk 
  about 
  0-51 
  in 
  length, 
  wanting 
  the 
  pelvic 
  fins. 
  The 
  

   anal 
  fin 
  is 
  displaced, 
  but 
  exhibits 
  both 
  the 
  series 
  of 
  basal 
  

   cartilages. 
  Purchased, 
  1860. 
  

  

  P. 
  3371 
  a. 
  Caudal 
  region 
  of 
  a 
  medium-sized 
  fish, 
  with 
  the 
  median 
  

   fins 
  somewhat 
  crushed 
  and 
  broken 
  and 
  remains 
  of 
  the 
  

   pelvic 
  pair. 
  Some 
  of 
  the 
  neural 
  spines 
  of 
  the 
  axial 
  

   skeleton 
  are 
  exhibited 
  beneath 
  the 
  supports 
  of 
  the 
  dorsal 
  

   fin 
  : 
  and 
  each 
  seen 
  in 
  front 
  view 
  shows 
  a 
  bifurcation 
  of 
  

   its 
  lower 
  extremity. 
  There 
  are 
  no 
  distinct 
  traces 
  of 
  

   haemal 
  arches 
  except 
  at 
  the 
  base 
  of 
  the 
  caudal 
  fin. 
  

  

  Enniskillen 
  Coll. 
  

  

  P. 
  3365. 
  Very 
  small 
  imperfect 
  caudal 
  region, 
  showing 
  the 
  pelvic, 
  

   anal, 
  and 
  caudal 
  fins. 
  Enniskillen 
  Coll. 
  

  

  P. 
  3365 
  a. 
  Dorsal 
  and 
  pelvic 
  fins 
  of 
  a 
  small 
  fish. 
  Enniskillen 
  Coll. 
  

  

  P. 
  7397. 
  Caudal 
  fin 
  of 
  moderate 
  size. 
  Purchased. 
  

  

  P. 
  3365 
  b. 
  Another 
  specimen, 
  wanting 
  the 
  extremity 
  of 
  the 
  upper 
  

   caudal 
  lobe. 
  Enniskillen 
  Coll. 
  

  

  39495. 
  Caudal 
  fin 
  0*28 
  in 
  depth, 
  displaying 
  the 
  caudal 
  fulcral 
  

   scales, 
  one 
  figured 
  in 
  Proc. 
  Geol. 
  Assoc, 
  vol. 
  xi. 
  pi. 
  i. 
  fig. 
  7. 
  

  

  Purchased, 
  1865. 
  

  

  P. 
  3368. 
  Two 
  examples 
  of 
  the 
  caudal 
  fin, 
  slightly 
  smaller. 
  

  

  Enniskillen 
  Coll. 
  

  

  Chondrosteus 
  pachyurus, 
  Egerton. 
  

  

  1858. 
  Chondrosteus 
  pachyurus, 
  Sir 
  P. 
  Egerton, 
  Phil. 
  Trans, 
  p. 
  883. 
  

  

  Type. 
  Tail 
  ; 
  Museum 
  of 
  Practical 
  Geology, 
  London. 
  

  

  The 
  undermentioned 
  specimens 
  indicate 
  a 
  fish 
  about 
  twice 
  as 
  

   large 
  as 
  the 
  ordinary 
  C. 
  acipenser 
  oides, 
  which 
  is 
  regarded 
  by 
  

   Egerton 
  as 
  specifically 
  distinct 
  from 
  the 
  latter. 
  So 
  far 
  as 
  known, 
  

   the 
  cranial 
  roof-bones 
  are 
  ornamented 
  with 
  closely-arranged 
  fine 
  

   tuberculations 
  ; 
  and 
  the 
  caudal 
  fulcral 
  scales 
  appear 
  to 
  be 
  rela- 
  

   tively 
  broader 
  than 
  those 
  of 
  the 
  type 
  species, 
  though 
  also 
  acuminate. 
  

  

  Form. 
  Sf 
  Loc. 
  Lower 
  Lias 
  : 
  Dorsetshire. 
  

  

  PART 
  III. 
  D 
  

  

  