﻿526 
  ACTINOPTERTGII. 
  

  

  and 
  rostral 
  region 
  wanting. 
  A 
  close 
  series 
  of 
  branchio- 
  

   stegal 
  rays 
  (br.) 
  is 
  indicated 
  on 
  the 
  side 
  figured, 
  while 
  the 
  

   large 
  dimensions 
  of 
  the 
  preoperculum 
  are 
  shown 
  by 
  the 
  

   counterpart. 
  The 
  vertebral 
  centra 
  are 
  longitudinally 
  

   split, 
  but 
  their 
  appended 
  arches 
  are 
  well 
  exhibited, 
  and 
  

   intermuscular 
  bones 
  are 
  very 
  numerous 
  in 
  the 
  dorsal 
  part 
  

   of 
  the 
  abdominal 
  region. 
  The 
  relative 
  proportions 
  of 
  the 
  

   paired 
  fins 
  are 
  indicated 
  by 
  fragments, 
  and 
  the 
  slender 
  

   proximal 
  ends 
  of 
  the 
  pair 
  of 
  pelvic 
  fin-supports 
  can 
  be 
  

   seen. 
  The 
  median 
  fins 
  are 
  imperfect, 
  but 
  the 
  origin 
  of 
  

   the 
  dorsal 
  fin 
  is 
  observed 
  to 
  be 
  opposite 
  that 
  of 
  the 
  anal 
  

   fin, 
  the 
  former 
  displaying 
  about 
  12 
  rays 
  and 
  the 
  latter 
  at 
  

   least 
  25 
  rays, 
  of 
  which 
  only 
  the 
  basal 
  ends 
  and 
  supports 
  

   remain. 
  The 
  lower 
  caudal 
  lobe 
  is 
  perfect 
  in 
  the 
  counter- 
  

   part, 
  from 
  which 
  it 
  is 
  restored 
  in 
  the 
  figure 
  ; 
  the 
  articular 
  

   dividing 
  lines 
  exhibit 
  the 
  characteristic 
  step-like 
  arrange- 
  

   ment. 
  Presented 
  by 
  F. 
  Harford, 
  Esq., 
  1888. 
  

  

  Thrissops 
  microdon, 
  Heckel. 
  

  

  1849-50. 
  Chirocentrites 
  microdon, 
  J. 
  J. 
  Heckel, 
  Sitzungsb. 
  k. 
  Akad. 
  

   Wiss., 
  math.-naturw. 
  01. 
  1849, 
  pt. 
  i. 
  p. 
  18, 
  and 
  Denkschr. 
  k. 
  Akad. 
  

   Wiss., 
  math.-naturw. 
  CI. 
  vol. 
  i. 
  p. 
  209, 
  pis. 
  xvi., 
  xvii. 
  

  

  1856. 
  Thrissops 
  microdon, 
  J. 
  J. 
  Heckel, 
  ibid. 
  vol. 
  xi. 
  p. 
  243. 
  

  

  1863. 
  Chirocentrites 
  microdon, 
  A. 
  Wagner, 
  Abh. 
  k. 
  bay. 
  Akad., 
  math.- 
  

   phys. 
  CI. 
  vol. 
  ix. 
  p. 
  734, 
  footnote. 
  

  

  1879. 
  Thrissops 
  microdon, 
  F. 
  Bassani,Verhandl. 
  k. 
  k. 
  geol. 
  Reichsanst. 
  

   p. 
  163. 
  

  

  1882. 
  Thrissops 
  microdon, 
  F. 
  Bassani, 
  Denkschr. 
  k. 
  Akad. 
  Wiss., 
  math.- 
  

   naturw. 
  CI. 
  vol. 
  xlv. 
  p. 
  208, 
  pi. 
  iii. 
  

  

  Type. 
  Head 
  aDd 
  abdominal 
  region 
  ; 
  Court 
  Museum, 
  Vienna. 
  

  

  A 
  species 
  attaining 
  a 
  length 
  of 
  about 
  0*45. 
  Length 
  of 
  head 
  with 
  

   opercular 
  apparatus 
  about 
  equalling 
  the 
  maximum 
  depth 
  of 
  the 
  

   trunk, 
  and 
  contained 
  seven 
  times 
  in 
  the 
  total 
  length 
  of 
  the 
  fish. 
  

   Vertebrae 
  at 
  least 
  60 
  in 
  number, 
  about 
  33 
  being 
  abdominal 
  and 
  27 
  

   caudal. 
  Pelvic 
  fins 
  nearly 
  twice 
  as 
  distant 
  from 
  the 
  pectorals 
  as 
  

   from 
  the 
  anal 
  ; 
  dorsal 
  fin, 
  with 
  about 
  14 
  rays, 
  arising 
  opposite 
  the 
  

   middle 
  of 
  the 
  anal, 
  which 
  is 
  much 
  elevated 
  in 
  front 
  and 
  comprises 
  

   nearly 
  40 
  rays 
  ; 
  caudal 
  fin 
  very 
  deeply 
  forked. 
  

  

  Form, 
  fy 
  Log. 
  Cretaceous 
  : 
  Isle 
  of 
  Lesina, 
  Dalmatia. 
  

  

  P. 
  7451. 
  Imperfect 
  fish 
  wanting 
  the 
  region 
  behind 
  the 
  origin 
  of 
  the 
  

   anal 
  fin. 
  Purchased, 
  1895. 
  

  

  