﻿408 
  

  

  ACTINOPTERYGII. 
  

  

  and 
  the 
  rostrum 
  much 
  laterally 
  compressed, 
  except 
  towards 
  its 
  

   attenuated 
  distal 
  extremity 
  which 
  is 
  round 
  in 
  section. 
  The 
  rounded 
  

   upper 
  contour 
  of 
  the 
  rostrum 
  gradually 
  becoming 
  raised 
  into 
  an 
  

   obtuse 
  median 
  longitudinal 
  ridge 
  at 
  its 
  base 
  and 
  ornamented 
  with 
  

   coarse 
  rugae, 
  which 
  frequently 
  subdivide 
  into 
  tubercles 
  and 
  are 
  

   mainly 
  longitudinal 
  in 
  direction 
  though 
  partly 
  turned 
  obliquely 
  

   downwards 
  ; 
  the 
  lateral 
  portions 
  ornamented 
  with 
  much 
  finer 
  

   longitudinal 
  rugae 
  which 
  in 
  part 
  tend 
  to 
  converge 
  at 
  the 
  middle 
  of 
  

   the 
  side, 
  and 
  form 
  a 
  slight 
  median 
  longitudinal 
  ridge 
  on 
  the 
  inferior 
  

   aspect 
  of 
  the 
  rostrum 
  for 
  some 
  distance 
  in 
  advance 
  of 
  the 
  vomerine 
  

   area. 
  

  

  Form. 
  $ 
  Loc. 
  Cenomanian 
  (Cambridge 
  Greensand) 
  : 
  Cambridge- 
  

   shire. 
  

  

  P. 
  7248. 
  Uncrushed 
  fragment 
  of 
  base 
  of 
  rostrum, 
  displaying 
  the 
  

   upper 
  contour 
  and 
  ornamentation, 
  the 
  pair 
  of 
  ethmoidal 
  

   canals, 
  and 
  part 
  of 
  the 
  vomerine 
  area. 
  Jesson 
  Coll. 
  

  

  P. 
  7246-47. 
  Five 
  typical 
  fragments 
  of 
  rostrum. 
  Jesson 
  Coll. 
  

  

  Protosphyrsena 
  brevirostris, 
  A. 
  S. 
  Woodward. 
  

  

  1895. 
  Protosphyrcena 
  brevirostris, 
  A. 
  S. 
  Woodward, 
  Geol. 
  Mag. 
  [4] 
  

   vol. 
  ii. 
  p. 
  212, 
  pi. 
  viii. 
  fig. 
  9. 
  

  

  Type. 
  Imperfect 
  rostrum 
  ; 
  British 
  Museum. 
  

  

  Rostrum 
  comparatively 
  short 
  and 
  acute, 
  its 
  length 
  apparently 
  

   not 
  exceeding 
  0*05 
  in 
  a 
  specimen 
  measuring 
  0*025 
  in 
  transverse 
  

   diameter 
  where 
  the 
  vomerine 
  teeth 
  are 
  implanted. 
  Upper 
  aspect 
  

   of 
  rostrum 
  flattened 
  and 
  the 
  sides 
  converging 
  below 
  in 
  a 
  median 
  

   inferior 
  keel, 
  making 
  the 
  transverse 
  section 
  triangular 
  at 
  the 
  end 
  of 
  

   the 
  vomerine 
  region 
  ; 
  surface 
  nearly 
  smooth. 
  

  

  Form. 
  Sf 
  Loc. 
  Cenomanian 
  (Cambridge 
  Greensand) 
  : 
  Cambridge- 
  

   shire. 
  

  

  P. 
  7253. 
  Type 
  specimen 
  described 
  and 
  figured, 
  loc. 
  cit. 
  Jesson 
  Coll. 
  

  

  P. 
  7252. 
  A 
  more 
  abraded 
  rostrum, 
  with 
  a 
  slightly 
  larger 
  and 
  longer 
  

   extension, 
  imperfect 
  at 
  the 
  extremity 
  but 
  exhibiting 
  a 
  

   flattened 
  triangular 
  area 
  immediately 
  in 
  front 
  of 
  the 
  

   vomerine 
  teeth, 
  noticed 
  ibid. 
  p. 
  214. 
  Jesson 
  Coll. 
  

  

  Protosphyrsena 
  depressa, 
  A. 
  S. 
  Woodward. 
  

   1895. 
  Protosphyrcena 
  depressa, 
  A. 
  S. 
  Woodward, 
  Geol. 
  Mag. 
  [4] 
  vol. 
  ii. 
  

   p. 
  212, 
  pi. 
  viii. 
  fig. 
  8. 
  

  

  Type. 
  Imperfect 
  rostrum 
  ; 
  Woodwardian 
  Museum, 
  Cambridge. 
  

   Rostrum 
  comparatively 
  short 
  and 
  depressed, 
  its 
  length 
  apparently 
  

  

  