﻿426 
  ACTINOPTEKYGTI. 
  

  

  opercular 
  apparatus 
  comprised 
  nearly 
  four-and-a-half 
  times 
  in 
  the 
  

   total 
  length 
  ; 
  maximum 
  depth 
  of 
  trunk 
  equalling 
  about 
  one-ninth 
  

   of 
  the 
  total 
  length 
  of 
  the 
  fish. 
  Cranium 
  rapidly 
  tapering 
  to 
  the 
  

   acute 
  rostrum, 
  which 
  is 
  produced 
  in 
  advance 
  of 
  the 
  mandible 
  to 
  equal 
  

   one-third 
  of 
  the 
  total 
  length 
  of 
  the 
  cranium 
  ; 
  cranial 
  bones 
  and 
  

   cheek-plates 
  ornamented 
  with 
  fine 
  granulations, 
  which 
  are 
  fused 
  

   into 
  longitudinal 
  rugae 
  on 
  the 
  rostrum 
  and 
  sometimes 
  on 
  part 
  of 
  

   the 
  cranial 
  roof; 
  mandible 
  and 
  opercular 
  bones 
  almost 
  smooth; 
  

   presymphysial 
  bone 
  very 
  short, 
  scarcely 
  longer 
  than 
  deep 
  ; 
  man- 
  

   dibular 
  teeth 
  very 
  robust. 
  Pelvic 
  fins 
  situated 
  far 
  behind 
  the 
  

   middle 
  point 
  of 
  the 
  trunk. 
  Scales 
  smooth, 
  except 
  those 
  of 
  the 
  

   dorsal 
  region, 
  which 
  are 
  marked 
  with 
  longitudinal 
  rugae. 
  

  

  The 
  " 
  single 
  row 
  of 
  small 
  close-set 
  tubercles," 
  noted 
  by 
  Egerton 
  

   on 
  the 
  ramus 
  of 
  the 
  mandible, 
  is 
  an 
  appearance 
  due 
  to 
  the 
  orifices 
  

   of 
  the 
  sensory 
  canal. 
  

  

  Form. 
  & 
  Log. 
  Purbeckian 
  : 
  Dorsetshire. 
  

  

  28621, 
  Head 
  and 
  abdominal 
  region, 
  lateral 
  and 
  partly 
  superior 
  

   aspect, 
  with 
  the 
  base 
  of 
  the 
  right 
  pectoral 
  fin 
  ; 
  Swanage. 
  

   In 
  the 
  mandible 
  the 
  presymphysial 
  bone 
  is 
  well 
  shown, 
  

   and 
  the 
  head 
  is 
  figured 
  in 
  Giinther's 
  ' 
  Introduction 
  to 
  the 
  

   Study 
  of 
  Pishes,' 
  p. 
  369, 
  fig. 
  146 
  (copied 
  in 
  Proc. 
  Geol. 
  

   Soc. 
  1884, 
  p. 
  50, 
  fig. 
  4). 
  Purchased, 
  1853. 
  

  

  P. 
  6380. 
  Imperfect 
  cranium 
  and 
  the 
  greater 
  portion 
  of 
  the 
  trunk, 
  

   much 
  fractured 
  ; 
  Swanage. 
  The 
  ornamentation 
  of 
  the 
  

   dorsal 
  scales 
  is 
  well 
  shown, 
  and 
  there 
  are 
  slight 
  traces 
  of 
  

   serrations 
  on 
  some 
  of 
  the 
  deep 
  flank-scales. 
  BecJcles 
  Coll. 
  

  

  Aspidorhynchus 
  crassus, 
  A. 
  S. 
  Woodward. 
  

   [Plate 
  XVII. 
  fig. 
  11.] 
  

  

  1844. 
  Sauropsis 
  mordax, 
  L. 
  Agassiz, 
  Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  ii. 
  p. 
  122 
  

  

  (name 
  only). 
  

   1871. 
  Pholidophorus 
  minor?, 
  J. 
  Phillips, 
  Geol. 
  Oxford, 
  p. 
  180, 
  

  

  woodc. 
  xlj 
  figs. 
  5, 
  6. 
  [Mandibular 
  ramus 
  ; 
  Oxford 
  Museum.] 
  

   (?) 
  1871. 
  Belonostomus 
  jlexuous, 
  J. 
  Phillips, 
  ibid. 
  fig. 
  3. 
  [Maxilla 
  ? 
  ; 
  

  

  Oxford 
  Museum.] 
  

   1888. 
  Aspidorhynchus 
  sp., 
  A. 
  S. 
  Woodward, 
  Arm. 
  Mag. 
  Nat. 
  Hist. 
  [6] 
  

  

  vol. 
  i. 
  p. 
  355. 
  

   1890. 
  Aspidorhynchus 
  crassus, 
  A. 
  S. 
  Woodward, 
  Proc. 
  Geol. 
  Assoc. 
  

  

  vol. 
  xi. 
  p. 
  295, 
  pi. 
  iii. 
  figs. 
  11-14. 
  

  

  Type. 
  Cranium 
  ; 
  British 
  Museum. 
  

  

  A 
  small 
  species 
  known 
  only 
  by 
  cranium 
  and 
  jaws. 
  Cranium 
  low, 
  

   gradually 
  tapering 
  to 
  the 
  acute 
  rostrum, 
  which 
  is 
  produced 
  in 
  

   advance 
  of 
  the 
  mandible 
  to 
  equal 
  one-third 
  of 
  the 
  total 
  length 
  of 
  

  

  