﻿semionottd^:. 
  67 
  

  

  trunk 
  and 
  smaller 
  head. 
  Dorsal 
  fin 
  considerably 
  longer 
  than 
  the 
  

   anal 
  and 
  not 
  remarkably 
  elevated. 
  

  

  Form. 
  Sf 
  Log. 
  Lower 
  Hawkesbury-Wianamatta 
  Series 
  (Upper 
  

   Trias) 
  : 
  Gosford, 
  New 
  South 
  Wales. 
  

  

  P. 
  6274. 
  Two 
  imperfect 
  fishes. 
  By 
  exchange, 
  1890. 
  

  

  Pristisomus 
  crassus, 
  A. 
  S. 
  Woodward. 
  

   1890. 
  Pristisomus 
  crassus, 
  A. 
  S. 
  Woodward, 
  op. 
  cit. 
  p. 
  36, 
  pi. 
  v. 
  

  

  figs. 
  5-7. 
  

  

  Type. 
  Nearly 
  complete 
  fish 
  ; 
  Geol. 
  Survey 
  Museum, 
  Sydney. 
  

  

  A 
  species 
  about 
  as 
  large 
  as 
  the 
  foregoing, 
  but 
  with 
  more 
  robust 
  

   and 
  less 
  deepened 
  trunk. 
  Head 
  with 
  opercular 
  apparatus 
  occupying 
  

   at 
  least 
  one-quarter 
  of 
  the 
  total 
  length 
  ; 
  maximum 
  depth 
  of 
  trunk 
  

   contained 
  about 
  three 
  times 
  in 
  the 
  total 
  length 
  of 
  the 
  fish. 
  Dorsal 
  

   fin 
  considerably 
  larger 
  than 
  the 
  anal, 
  as 
  long 
  as 
  deep. 
  

  

  Form. 
  Sf 
  Log. 
  Lower 
  Hawkesbury-Wianamatta 
  Series 
  (Upper 
  

   Trias) 
  : 
  Gosford, 
  New 
  South 
  Wales. 
  

  

  P. 
  6276. 
  Trunk 
  showing 
  dorsal 
  and 
  part 
  of 
  caudal 
  fin. 
  

  

  By 
  exchange, 
  1890. 
  

  

  P. 
  6277. 
  Slab 
  with 
  nearly 
  complete 
  fish, 
  associated 
  with 
  P. 
  gracilis. 
  

  

  By 
  exchange, 
  1890. 
  

  

  Genus 
  SARGODON, 
  Plieninger. 
  

   [Wiirtt. 
  Jahresh. 
  vol. 
  iii. 
  1847, 
  p. 
  165.] 
  

  

  An 
  indefinable 
  genus 
  known 
  only 
  by 
  the 
  external 
  incisive 
  teeth. 
  

   The 
  dental 
  crown 
  is 
  sharply 
  separated 
  from 
  the 
  long, 
  cylindrical 
  or 
  

   nearly 
  quadrangular 
  root, 
  and 
  is 
  chisel-like 
  in 
  shape. 
  

  

  It 
  seems 
  probable 
  that 
  the 
  fish 
  possessing 
  such 
  teeth 
  would 
  also 
  

   have 
  tritoral 
  teeth 
  on 
  the 
  inner 
  bones 
  of 
  the 
  mouth. 
  As 
  originally 
  

   suggested 
  by 
  Plieninger, 
  it 
  is, 
  therefore, 
  not 
  unlikely 
  that 
  the 
  small 
  

   Bhsetic 
  teeth 
  named 
  Psammodus 
  orbicularis 
  (Meyer 
  & 
  Plieninger, 
  

   Beitr. 
  Pal. 
  Wiirttembergs, 
  1844, 
  p. 
  117, 
  pi. 
  x. 
  fig. 
  24), 
  and 
  others 
  

   ascribed 
  to 
  Sphairodus 
  minimus 
  (ibid. 
  p. 
  117, 
  pi. 
  x. 
  fig. 
  23, 
  named 
  

   by 
  Agassiz, 
  Poiss. 
  Poss. 
  vol. 
  ii. 
  pt. 
  ii. 
  1844, 
  pp. 
  216, 
  300), 
  truly 
  

   belong 
  to 
  Sargodon. 
  Similar 
  tritoral 
  teeth 
  have 
  been 
  described 
  from 
  

   the 
  RhEetic 
  of 
  Leicestershire 
  (A. 
  S. 
  Woodward, 
  Trans. 
  Leicester 
  Lit. 
  

   & 
  Phil. 
  Soc, 
  n. 
  s. 
  vol. 
  i. 
  pt. 
  xi. 
  1889, 
  p. 
  20), 
  Somersetshire, 
  and 
  

   Gloucestershire 
  (M. 
  Browne, 
  Eep. 
  Brit. 
  Assoc. 
  1891, 
  p. 
  645), 
  and 
  

   some 
  are 
  preserved 
  in 
  the 
  Collection 
  from 
  Aust 
  Cliff, 
  near 
  Bristol 
  

   (P. 
  6069 
  a. 
  Presented 
  by 
  F. 
  Harford, 
  Esq., 
  1889). 
  

  

  f2 
  

  

  