﻿MACKOSEMIID^. 
  

  

  165 
  

  

  Back 
  elevated 
  and 
  angulated 
  anteriorly, 
  the 
  

   dorsal 
  fin 
  extending 
  from 
  the 
  angula- 
  

   tion 
  almost 
  to 
  the 
  caudal 
  fin, 
  which 
  is 
  

   deeply 
  forked 
  ; 
  uniserial 
  fulcra 
  on 
  both 
  

   paired 
  and 
  median 
  fins; 
  squamation 
  

   complete 
  and 
  flank-scales 
  deepened 
  . 
  , 
  Histionotus 
  (p. 
  173) 
  r 
  

  

  Back 
  nearly 
  straight, 
  and 
  dorsal 
  fin 
  extend- 
  

   ing 
  almost 
  its 
  whole 
  length 
  ; 
  squama- 
  

   tion 
  apparently 
  complete, 
  the 
  flank- 
  

   scales 
  very 
  large 
  and 
  much 
  deepened. 
  . 
  Legnonotus 
  (p. 
  176). 
  

  

  Back 
  nearly 
  straight, 
  and 
  dorsal 
  fin 
  extend- 
  

   ing 
  almost 
  its 
  whole 
  length 
  ; 
  caudal 
  fin 
  

   not 
  forked, 
  rounded 
  ; 
  fulcra 
  only 
  on 
  the 
  

   caudal 
  fin 
  ; 
  scales 
  thin, 
  wanting 
  dorsally 
  

   and 
  ventrally, 
  those 
  of 
  the 
  flank 
  scarcely 
  

   deepened 
  and 
  the 
  vertical 
  series 
  dicho- 
  

   tomous 
  above 
  ; 
  much-enlarged 
  ridge- 
  

   scales 
  on 
  lower 
  border 
  of 
  caudal 
  pedicle. 
  Macrosemius 
  (p. 
  176)* 
  

  

  Back 
  nearly 
  straight, 
  and 
  dorsal 
  fin 
  extend- 
  

   ing 
  almost 
  its 
  whole 
  length 
  ; 
  (?) 
  no 
  anal 
  

   fin 
  ; 
  squamation 
  robust 
  and 
  complete, 
  

   but 
  irregular, 
  the 
  flank-scales 
  not 
  much 
  

   if 
  at 
  all 
  deepened, 
  the 
  vertical 
  series 
  

   apparently 
  sometimes 
  dichotomous 
  

  

  dorsally 
  and 
  ventrally 
  Petalopteryx 
  (p. 
  181). 
  

  

  II. 
  Dorsal 
  fin 
  subdivided 
  into 
  two 
  parts. 
  

  

  Vertebral 
  rings 
  feeble 
  or 
  absent; 
  anterior 
  

   portion 
  of 
  dorsal 
  deeper 
  than 
  the 
  pos- 
  

   terior 
  portion 
  ; 
  squamation 
  complete 
  . 
  . 
  Propterus 
  (p. 
  183). 
  

  

  Vertebral 
  rings 
  robust; 
  anterior 
  portion 
  of 
  

   dorsal 
  with 
  comparatively 
  widely 
  spaced 
  

   rays, 
  not 
  deeper 
  than 
  the 
  posterior 
  por- 
  

   tion 
  ; 
  squamation 
  complete 
  Notagogus 
  (p. 
  186). 
  

  

  Genus 
  OPHIOPSIS, 
  

  

  [STeues 
  Jahrb. 
  1834, 
  p. 
  385.] 
  

  

  Trunk 
  much 
  elongated, 
  gradually 
  tapering 
  from 
  the 
  occiput 
  back- 
  

   wards 
  or 
  the 
  dorsal 
  margin 
  only 
  slightly 
  arcuate 
  ; 
  head 
  large 
  or 
  of 
  

   moderate 
  size. 
  Marginal 
  teeth 
  acutely 
  pointed. 
  Notochord 
  invested 
  

   with 
  delicate 
  ring- 
  vertebrae 
  ; 
  ribs 
  ossified. 
  Bifurcation 
  of 
  dorsal 
  

   fin-rays 
  variable 
  ; 
  fulcra 
  often 
  absent 
  on 
  paired 
  fins 
  and 
  usually- 
  

   confined 
  to 
  the 
  base 
  of 
  the 
  median 
  fins. 
  Paired 
  fins 
  relatively 
  

   large 
  ; 
  dorsal 
  fin 
  ordinarily 
  extending 
  about 
  half 
  the 
  length 
  of 
  the 
  

   back, 
  high 
  in 
  front, 
  low 
  behind 
  ; 
  anal 
  fin 
  small 
  ; 
  caudal 
  fin 
  forked. 
  

   Scales 
  covering 
  the 
  whole 
  of 
  the 
  trunk, 
  in 
  regular 
  series, 
  united 
  by 
  

  

  