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  A.CTINOPTERYGII. 
  

  

  suboperculum 
  is 
  both 
  broad 
  and 
  remarkably 
  long. 
  The 
  

   teeth 
  are 
  partly 
  acuminate, 
  partly 
  round; 
  but 
  it 
  is 
  

   probable 
  that 
  most 
  of 
  the 
  latter 
  owe 
  their 
  form 
  to 
  wear. 
  

   The 
  principal 
  flank-scales 
  are 
  serrated, 
  and 
  the 
  fluted 
  

   structure 
  is 
  shown 
  in 
  all 
  the 
  scales 
  from 
  which 
  the 
  

   enamelled 
  surface 
  has 
  been 
  removed. 
  Purchased, 
  1886. 
  

  

  20673 
  a. 
  A 
  much 
  crushed 
  and 
  abraded 
  head, 
  with 
  the 
  anterior 
  

   portion 
  of 
  the 
  abdominal 
  region, 
  the 
  type 
  specimen 
  of 
  the 
  

   so-called 
  L.fittoni, 
  figured 
  by 
  Agassiz, 
  torn. 
  cit. 
  pi. 
  xxx. 
  a. 
  

   fig. 
  1 
  ; 
  Highfure, 
  Billingshurst. 
  The 
  mandibular 
  rami 
  

   differ 
  from 
  those 
  of 
  the 
  preceding 
  specimen 
  in 
  having 
  

   their 
  inferior 
  margin 
  considerably 
  curved 
  downwards 
  to 
  a 
  

   point 
  at 
  the 
  symphysis. 
  The 
  openings 
  in 
  the 
  scales 
  of 
  

   the 
  dorsal 
  region 
  for 
  sensory 
  canals 
  are 
  not 
  very 
  regularly 
  

   arranged. 
  Presented 
  by 
  P. 
  J. 
  Martin, 
  Esq., 
  1846. 
  

  

  43073. 
  A 
  much 
  more 
  imperfect, 
  crushed 
  specimen 
  ; 
  East 
  Grinstead. 
  

  

  Purchased, 
  1871. 
  

  

  P. 
  6933. 
  Fine 
  example 
  of 
  the 
  head 
  and 
  anterior 
  abdominal 
  region 
  of 
  

   a 
  young 
  individual, 
  shown 
  of 
  one-half 
  the 
  natural 
  size 
  from 
  

   the 
  superior 
  (a) 
  and 
  left 
  lateral 
  (6) 
  aspects 
  in 
  the 
  accom- 
  

   panying 
  fig. 
  23; 
  Hastings. 
  The 
  extremity 
  of 
  the 
  snout 
  

   is 
  broken 
  away, 
  and 
  only 
  a 
  doubtful 
  fragment 
  of 
  bone 
  

   appears 
  to 
  represent 
  the 
  maxilla 
  (moo.) 
  on 
  the 
  left 
  side. 
  

   The 
  cranial 
  roof-bones 
  are 
  in 
  part 
  coarsely 
  rugose 
  and 
  

   ornamented 
  with 
  very 
  fine 
  tuberculations, 
  mostly 
  in 
  radi- 
  

   ating 
  lines 
  ; 
  the 
  supratemporal 
  plates 
  (s.t.) 
  are 
  arranged 
  in 
  

   four 
  pairs, 
  the 
  two 
  innermost 
  not 
  quite 
  symmetrical 
  and 
  

   representing 
  the 
  single 
  pair 
  in 
  adults. 
  The 
  mandible 
  is 
  

   shown, 
  partly 
  smooth, 
  partly 
  with 
  the 
  characteristic 
  coarse 
  

   rugosity 
  ; 
  and 
  the 
  inferior 
  border 
  of 
  the 
  dentary 
  bone 
  (d.) 
  

   is 
  very 
  sharply 
  curved 
  downwards 
  to 
  a 
  point 
  at 
  the 
  

   mandibular 
  symphysis. 
  The 
  circumorbital 
  (c.o.), 
  sub- 
  

   orbital 
  (5.0.), 
  and 
  opercular 
  bones 
  are 
  well 
  preserved 
  on 
  

   the 
  left 
  side 
  ; 
  the 
  first 
  two 
  series 
  marked 
  with 
  a 
  few 
  

   large 
  tubercles 
  in 
  their 
  lower 
  portion, 
  more 
  delicately 
  

   ornamented 
  above, 
  and 
  the 
  opercular 
  bones 
  very 
  finely 
  

   granulated. 
  The 
  maximum 
  width 
  of 
  the 
  operculum 
  (op.) 
  

   is 
  two-thirds 
  as 
  great 
  as 
  its 
  depth, 
  and 
  its 
  anterior 
  margin 
  

   is 
  sinuous, 
  exhibiting 
  a 
  considerable 
  concavity 
  above 
  ; 
  

   the 
  maximum 
  depth 
  of 
  the 
  suboperculum 
  (s.op.) 
  is 
  about 
  

   half 
  that 
  of 
  the 
  operculum, 
  and 
  its 
  anterior 
  ascending 
  

  

  