﻿pycnodontid^:. 
  197 
  

  

  tion 
  of 
  the 
  tritoral 
  teeth 
  to 
  a 
  fixed 
  arrangement 
  in 
  regular 
  longi- 
  

   tudinal 
  series 
  ; 
  and 
  (iir.) 
  in 
  the 
  obliteration 
  of 
  the 
  indent 
  for 
  the 
  

   meckelian 
  cartilage 
  on 
  the 
  attached 
  face 
  of 
  the 
  splenial 
  hone. 
  Very 
  

   rarely 
  (Coccodus, 
  Xenojpholis) 
  a 
  spinous 
  dermal 
  armour 
  is 
  also 
  

   developed. 
  Finally, 
  we 
  venture 
  to 
  recognize 
  one 
  case 
  of 
  degeneracy 
  

   of 
  the 
  tritoral 
  dentition 
  (Anomoeodus). 
  

  

  Synopsis 
  of 
  Genera. 
  

  

  I. 
  Neural 
  and 
  haemal 
  arches 
  of 
  axial 
  skeleton 
  of 
  

  

  trunk 
  not 
  expanding 
  sufficiently 
  to 
  encircle 
  

  

  the 
  notochord. 
  

  

  (a.) 
  Number 
  of 
  longitudinal 
  series 
  of 
  teeth 
  

  

  on 
  splenial 
  bone 
  inconstant 
  ; 
  caudal 
  fin 
  

  

  rounded 
  ; 
  no 
  dermal 
  spines. 
  

  

  Vomerine 
  teeth 
  in 
  five 
  longitudinal 
  series, 
  

  

  sometimes 
  irregular 
  laterally 
  ; 
  splenial 
  

  

  dentition 
  comprising 
  one 
  regular 
  

  

  principal 
  series, 
  with 
  three 
  or 
  more 
  

  

  outer 
  series 
  and 
  one 
  or 
  two 
  inner 
  

  

  series, 
  usually 
  irregularly 
  arranged 
  ; 
  

  

  scales 
  tuber 
  culated, 
  confined 
  to 
  region 
  

  

  in 
  advance 
  of 
  median 
  fins 
  Mesodon 
  (p. 
  199). 
  

  

  [Splenial 
  dentition 
  as 
  in 
  Mesodon, 
  but 
  

  

  usually 
  much 
  more 
  irregularly 
  ar- 
  

   ranged, 
  and 
  the 
  principal 
  longitudinal 
  

  

  series 
  not 
  well 
  - 
  differentiated 
  ; 
  the 
  

  

  splenial 
  bone 
  much 
  stouter, 
  and 
  with 
  a 
  

  

  remarkably 
  deep 
  symphysial 
  facette; 
  

  

  fish 
  unknown 
  Athrodon 
  (p. 
  215).] 
  

  

  Vomerine 
  teeth 
  in 
  three 
  regular 
  longitu- 
  

   dinal 
  series, 
  with 
  irregular 
  interme- 
  

   diate 
  series 
  j 
  splenial 
  dentition 
  with 
  

  

  two 
  regular 
  series 
  separated 
  by 
  small 
  

  

  teeth, 
  and 
  flanked 
  within 
  by 
  other 
  

  

  small 
  teeth 
  ; 
  scales 
  covering 
  whole 
  of 
  

  

  trunk, 
  united 
  above 
  and 
  below 
  with 
  

  

  jagged 
  sutures 
  Mesturus 
  (p. 
  218). 
  

  

  (I.) 
  Number 
  of 
  longitudinal 
  series 
  of 
  teeth 
  

   on 
  splenial 
  bone 
  constant; 
  caudal 
  fin 
  

   forked 
  ; 
  no 
  dermal 
  spines. 
  

   Vomerine 
  teeth 
  in 
  five 
  longitudinal 
  series, 
  

  

  the 
  inner 
  lateral 
  pairs 
  regularly 
  alter- 
  

   nating 
  with 
  the 
  widely-spaced 
  median 
  

  

  teeth; 
  splenial 
  teeth 
  in 
  four 
  regular 
  

  

  series 
  ; 
  squamation 
  confined 
  almost 
  or 
  

  

  completely 
  to 
  region 
  in 
  advance 
  of 
  

  

  median 
  fins 
  Microdon, 
  p. 
  221). 
  

  

  