﻿LEPTOLEPID.E. 
  501 
  

  

  Genus 
  LEPTQLEPIS, 
  Agassiz. 
  

   [Neues 
  Jahrb. 
  1832, 
  p. 
  146.] 
  

  

  Syn. 
  Ascalabos, 
  G. 
  von 
  Miinster, 
  Beitr. 
  Petrefakt. 
  pt. 
  i. 
  1839, 
  p. 
  112 
  

   (undefined). 
  

   Tharsis, 
  C. 
  G. 
  Giebel, 
  Fauna 
  d. 
  Vorwelt, 
  Fische, 
  1848, 
  p. 
  145. 
  

   Sarginites, 
  0. 
  G. 
  Costa, 
  Atti 
  Accad. 
  Pontan. 
  vol. 
  v. 
  1850, 
  p. 
  285. 
  

   Megastoma, 
  0. 
  G. 
  Costa, 
  ibid. 
  1850, 
  p. 
  287. 
  

  

  Head 
  large 
  and 
  teeth 
  minute 
  ; 
  sclerotic 
  ossified. 
  Maxilla 
  arched, 
  

   with 
  a 
  slightly 
  convex 
  dentigerous 
  border; 
  mandible 
  prominent, 
  

   and 
  dentary 
  sharply 
  rising 
  into 
  a 
  thickened, 
  obtuse 
  elevation 
  near 
  

   its 
  anterior 
  extremity 
  ; 
  preoperculum 
  broad 
  mesially, 
  with 
  a 
  large 
  

   inferior 
  limb, 
  marked 
  with 
  radiating 
  ridges 
  ; 
  suboperculum 
  large, 
  

   but 
  smaller 
  than 
  the 
  trapezoidal 
  operculum, 
  from 
  which 
  it 
  is 
  divided 
  

   by 
  an 
  oblique 
  suture. 
  Vertebrae 
  in 
  the 
  form 
  of 
  much-constricted 
  

   cylinders, 
  with 
  little 
  or 
  no 
  secondary 
  ossification. 
  Pelvic 
  fins 
  rela- 
  

   tively 
  large 
  ; 
  dorsal 
  fin 
  about 
  as 
  long 
  as 
  deep, 
  opposed 
  to 
  the 
  pelvic 
  

   pair 
  or 
  to 
  the 
  space 
  between 
  the 
  latter 
  and 
  the 
  anal 
  ; 
  anal 
  fin 
  small, 
  

   not 
  much 
  extended 
  ; 
  caudal 
  fin 
  deeply 
  forked. 
  Scales 
  completely 
  

   covering 
  the 
  trunk 
  ; 
  no 
  enlarged 
  or 
  thickened 
  ridge-scales. 
  

  

  The 
  external 
  bones 
  and 
  scales 
  are 
  covered 
  with 
  a 
  very 
  thin 
  layer 
  

   of 
  ganoine, 
  always 
  smooth 
  or 
  only 
  feebly 
  rugose. 
  The 
  cranial 
  roof 
  

   is 
  flattened 
  in 
  the 
  middle, 
  abruptly 
  truncated 
  behind, 
  and 
  very 
  

   narrow 
  between 
  the 
  orbits 
  ; 
  the 
  parietals 
  are 
  very 
  small, 
  and 
  the 
  

   suture 
  between 
  the 
  much-elongated 
  frontals 
  is 
  wavy. 
  The 
  para- 
  

   sphenoid 
  is 
  delicate. 
  There 
  is 
  a 
  series 
  of 
  large 
  suborbital 
  bones, 
  

   and 
  the 
  sensory 
  canal 
  traversing 
  them 
  exhibits 
  a 
  number 
  of 
  short 
  

   branches 
  radiating 
  downwards. 
  This 
  is 
  observable 
  both 
  behind 
  and 
  

   in 
  front 
  of 
  the 
  orbit. 
  The 
  sclerotic 
  ring 
  is 
  ossified. 
  The 
  premaxilla 
  

   is 
  small, 
  and 
  the 
  long 
  curved 
  maxilla, 
  having 
  minute 
  teeth 
  on 
  its 
  

   convex 
  oral 
  margin, 
  is 
  contracted, 
  though 
  comparatively 
  robust, 
  at 
  

   its 
  loose 
  anterior 
  articulation. 
  There 
  are 
  also 
  two 
  elongated 
  supra- 
  

   maxillary 
  bones, 
  deeply 
  overlapping 
  the 
  maxilla. 
  The 
  mandible 
  is 
  

   deep 
  in 
  the 
  middle, 
  and 
  consists 
  almost 
  entirely 
  (if 
  not 
  entirely) 
  of 
  

   two 
  elements. 
  The 
  robust 
  dentary 
  bone 
  is 
  remarkable 
  for 
  the 
  deep 
  

   coronoid 
  process 
  rising 
  nearest 
  its 
  anterior 
  end 
  ; 
  behind, 
  and 
  partly 
  

   above 
  it, 
  is 
  the 
  large 
  laminar 
  angulo-articular 
  element. 
  The 
  cera- 
  

   tohyal 
  has 
  the 
  ordinary 
  hour-glass 
  form, 
  but 
  is 
  noteworthy 
  for 
  the 
  

   extension 
  of 
  a 
  supplementary 
  delicate 
  straight 
  rod 
  of 
  bone 
  between 
  

   its 
  extremities 
  on 
  the 
  upper 
  side. 
  The 
  opercular 
  apparatus 
  is 
  

   complete, 
  and 
  the 
  sensory 
  canal 
  upon 
  the 
  preoperculum 
  exhibits 
  

   radiating 
  branches 
  resembling 
  those 
  of 
  the 
  suborbital 
  line, 
  The 
  

   branchiostegal 
  rays 
  on 
  the 
  short 
  epihyal 
  are 
  broad 
  and 
  imbricating, 
  

   while 
  those 
  supported 
  by 
  the 
  ceratohyal 
  are 
  spaced 
  and 
  delicate 
  ; 
  

  

  