﻿252 
  ACTTNOPTERYGII. 
  

  

  middle 
  point 
  between 
  the 
  dorsal 
  and 
  ventral 
  borders 
  of 
  the 
  fish. 
  

   11 
  vertical 
  series 
  of 
  scales. 
  

  

  The 
  splenial 
  dentition 
  named 
  Pycnodus 
  achillis 
  is 
  characterized 
  

   thus 
  : 
  — 
  Teeth 
  of 
  principal 
  series 
  at 
  least 
  twice 
  as 
  broad 
  as 
  long, 
  

   exceeding 
  in 
  width 
  the 
  two 
  outer 
  series 
  and 
  irregularly 
  bordered 
  

   within 
  by 
  one 
  row 
  of 
  small 
  round 
  teeth 
  ; 
  those 
  of 
  the 
  inner 
  flanking 
  

   series 
  also 
  at 
  least 
  twice 
  as 
  broad 
  as 
  long, 
  sometimes 
  subdivided 
  ; 
  

   those 
  of 
  the 
  outermost 
  series 
  small 
  and 
  round. 
  

  

  Form. 
  Sf 
  Log. 
  Cretaceous 
  : 
  Pietraroja, 
  Naples. 
  

  

  Not 
  represented 
  in 
  the 
  Collection. 
  

  

  Coelodus 
  costse, 
  Heckel. 
  

  

  1850. 
  Pycnodus 
  rhombus, 
  0. 
  G. 
  Costa 
  (errore), 
  Atti 
  Accad. 
  Pontan. 
  

  

  vol. 
  v. 
  p. 
  332, 
  pi. 
  iv. 
  fig. 
  8 
  (non 
  pi. 
  v. 
  fig. 
  1). 
  

   1856. 
  Coelodus 
  costcs, 
  J. 
  J. 
  Heckel, 
  Denkschr. 
  k. 
  Akad. 
  Wiss., 
  math.- 
  

  

  naturw. 
  CI. 
  vol. 
  xi. 
  p. 
  203. 
  

  

  Type. 
  Nearly 
  complete 
  fish. 
  

  

  A 
  small 
  species 
  attaining 
  a 
  length 
  of 
  about 
  0*105. 
  Maximum 
  

   depth 
  of 
  the 
  trunk 
  much 
  exceeding 
  one-half, 
  and 
  length 
  of 
  head 
  

   with 
  opercular 
  apparatus 
  equalling 
  one-third 
  of 
  the 
  total 
  length 
  of 
  

   the 
  fish. 
  Teeth 
  of 
  principal 
  (inner) 
  series 
  on 
  splenial 
  about 
  three 
  

   times 
  as 
  broad 
  as 
  long, 
  indented 
  on 
  the 
  apex 
  and 
  with 
  crenulated 
  

   margin. 
  Dorsal 
  fin 
  with 
  about 
  46 
  rays, 
  occupying 
  more 
  than 
  half 
  

   of 
  the 
  back 
  ; 
  anal 
  fin 
  with 
  about 
  35 
  rays, 
  arising 
  more 
  posteriorly. 
  

   10-12 
  vertical 
  series 
  of 
  scales. 
  

  

  Form. 
  Sf 
  Log. 
  Upper 
  Jurassic 
  : 
  S. 
  Italy. 
  

  

  P. 
  1671 
  a. 
  Small 
  specimen 
  displaying 
  median 
  fins 
  and 
  a 
  few 
  of 
  the 
  

   splenial 
  teeth 
  ; 
  Torre 
  d'Orlando, 
  near 
  Naples. 
  

  

  Egerton 
  Coll. 
  

  

  P. 
  4394. 
  More 
  imperfectly 
  preserved 
  fish, 
  0*105 
  in 
  length, 
  also 
  

  

  mdo. 
  

   Fnniskillen 
  Coll. 
  

  

  showing 
  some 
  of 
  the 
  teeth 
  ; 
  Torre 
  d'Orlando. 
  

  

  Coelodus 
  mantelli 
  (Agassiz). 
  

  

  1827. 
  " 
  Palates 
  of 
  an 
  unknown 
  fish," 
  G. 
  A. 
  Mantell, 
  Foss. 
  Tilgate 
  

  

  Forest, 
  p. 
  58, 
  pi. 
  xvii. 
  figs. 
  26, 
  27. 
  

   1833. 
  Pycnodus 
  microdon, 
  L. 
  Agassiz, 
  Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  i. 
  p. 
  17. 
  

   1839-44. 
  Pycnodus 
  mantellii, 
  L. 
  Agassiz, 
  ibid. 
  pt. 
  ii. 
  p. 
  196, 
  pi. 
  lxxii. 
  a. 
  

  

  figs. 
  6-14. 
  

   1839-44. 
  Gyrodus 
  mantellii, 
  L. 
  Agassiz, 
  ibid. 
  pt. 
  ii. 
  p. 
  234, 
  pi. 
  lxix. 
  a. 
  

  

  fig. 
  18. 
  [Splenial 
  ; 
  British 
  Museum.] 
  

  

  