﻿ptcxodontidj:. 
  221 
  

  

  forinable 
  with 
  the 
  vertical 
  flank-series, 
  are 
  observed 
  at 
  

   the 
  base 
  of 
  the 
  lobe 
  of 
  the 
  pectoral 
  fin 
  ; 
  while 
  those 
  of 
  

   the 
  gular 
  and 
  branchiostegal 
  region 
  have 
  already 
  been 
  

   noticed. 
  Hdherlein 
  Coll. 
  

  

  Mesturas 
  leedsi, 
  sp. 
  nov. 
  

  

  Type. 
  Imperfect 
  head 
  and 
  trunk 
  : 
  collection 
  of 
  Alfred 
  X. 
  Leeds, 
  

   Esq., 
  Eyebury. 
  

  

  A 
  larger 
  species 
  than 
  M. 
  verrucosus, 
  with 
  more 
  coarsely 
  and 
  

   sparsely 
  tuberculated 
  scales, 
  which 
  do 
  not 
  exhibit 
  any 
  radiating 
  

   lines. 
  Xo 
  enlarged 
  tubercles 
  on 
  the 
  course 
  of 
  the 
  lateral 
  line. 
  

   Premaxilla 
  with 
  three, 
  dentary 
  with 
  four 
  prehensile 
  teeth. 
  Vome- 
  

   rine 
  and 
  splenial 
  teeth 
  smooth, 
  exhibiting 
  a 
  shallow 
  apical 
  indenta- 
  

   tion 
  with 
  a 
  crimped 
  margin, 
  very 
  rarely 
  also 
  with 
  a 
  slight 
  median 
  

   tubercle 
  ; 
  shape 
  of 
  indentation 
  varying 
  with 
  that 
  of 
  the 
  tooth, 
  and 
  

   the 
  hinder 
  portion 
  of 
  its 
  crimped 
  border 
  not 
  infrequently 
  wanting. 
  

   Oral 
  surface 
  of 
  vomer 
  flat, 
  with 
  outer 
  lateral 
  teeth 
  not 
  much 
  

   inferior 
  in 
  size 
  to 
  those 
  of 
  the 
  median 
  series 
  ; 
  inner 
  lateral 
  teeth 
  

   less 
  than 
  half 
  as 
  large 
  as 
  these, 
  very 
  irregular 
  and 
  much 
  supple- 
  

   mented 
  behind. 
  Splenial 
  dentition 
  comprising 
  one 
  principal 
  longi- 
  

   tudinal 
  series 
  of 
  teeth, 
  all 
  oval 
  and 
  about 
  as 
  large 
  as 
  the 
  median 
  

   vomerine 
  teeth, 
  but 
  with 
  long 
  axis 
  oblique; 
  outermost 
  series 
  

   regular 
  and 
  similar, 
  but 
  rather 
  smaller 
  ; 
  one 
  regular 
  row 
  of 
  round 
  

   teeth 
  about 
  half 
  as 
  large, 
  and 
  an 
  innermost 
  irregular 
  row 
  of 
  still 
  

   smaller 
  teeth, 
  within 
  the 
  principal 
  series 
  ; 
  two 
  similar 
  rows 
  of 
  

   small 
  teeth 
  also 
  interposed 
  between 
  the 
  latter 
  and 
  the 
  outermost 
  

   series, 
  but 
  these 
  again 
  irregularly 
  supplemented 
  in 
  the 
  hinder 
  two- 
  

   thirds 
  of 
  the 
  bone. 
  

  

  Form. 
  Sf 
  Log. 
  Oxfordian 
  : 
  Huntingdonshire. 
  

  

  P. 
  6834. 
  Associated 
  series 
  of 
  bones 
  isolated 
  from 
  matrix 
  ; 
  Oxford 
  

   Clay, 
  near 
  Peterborough. 
  In 
  the 
  nomenclature 
  here 
  

   adopted 
  the 
  series 
  comprises 
  the 
  parasphenoid, 
  basi- 
  

   sphenoid, 
  right 
  postfrontal, 
  right 
  and 
  left 
  squamosal, 
  

   portion 
  of 
  right 
  frontal, 
  right 
  and 
  left 
  operculum, 
  and 
  

   other 
  fragments. 
  Leeds 
  Coll. 
  

  

  Genus 
  MICRODON, 
  Agassiz 
  1 
  .-- 
  

   [Poiss. 
  Foss. 
  vol. 
  ii. 
  pt. 
  i. 
  1833, 
  p. 
  16, 
  pt. 
  ii. 
  1844, 
  p. 
  204.] 
  

  

  Trunk 
  deeply 
  fusiform, 
  often 
  almost 
  discoidal, 
  with 
  a 
  slender 
  

   abbreviated 
  caudal 
  pedicle. 
  Head 
  and 
  opercular 
  bones 
  ornamented 
  

  

  1 
  This 
  name 
  having 
  gained 
  universal 
  acceptance, 
  we 
  adopt 
  it, 
  notwithstanding 
  

   its 
  preoccupation 
  among 
  Diptera 
  by 
  Microdon, 
  Meigen, 
  1803. 
  

  

  