﻿SEMTONOTID^. 
  51 
  

  

  Trunk 
  irregularly 
  cycloidal, 
  with 
  

   strongly-arched 
  back 
  ; 
  marginal 
  

   teeth 
  slender 
  and 
  styliform 
  ; 
  dor- 
  

   sal 
  and 
  anal 
  fins 
  opposed, 
  not 
  

   much 
  extended 
  : 
  all 
  scales 
  rhom- 
  

   bic, 
  with 
  thick 
  inner 
  rib, 
  very 
  

   deep 
  and 
  narrow 
  on 
  flank 
  ; 
  ridge 
  - 
  

   scales 
  conspicuous 
  Cleithrolepis 
  (p. 
  154). 
  

  

  Trunk 
  irregularly 
  cycloidal, 
  with 
  

   strongly-arched 
  back; 
  dorsal 
  fin 
  

   much 
  extended 
  and 
  anal 
  opposed 
  

   to 
  its 
  hinder 
  portion 
  ; 
  abdominal 
  

   scales 
  rhombic, 
  with 
  thick 
  inner 
  

   rib 
  ; 
  caudal 
  scales 
  more 
  or 
  less 
  

   cycloidal 
  Aetheolepis 
  (p. 
  157). 
  

  

  Trunk 
  irregularly 
  cycloidal, 
  with 
  ab- 
  

   dominal 
  protuberance 
  ; 
  marginal 
  

   teeth 
  slender 
  and 
  styliform 
  ; 
  dorsal 
  

   fin 
  much 
  extended 
  and 
  anal 
  op- 
  

   posed 
  to 
  its 
  hinder 
  half 
  ; 
  all 
  scales 
  

   rhombic, 
  with 
  thick 
  inner 
  rib, 
  but 
  

   those 
  of 
  caudal 
  region 
  compara- 
  

   tively 
  delicate 
  ; 
  ventral 
  ridge- 
  

   scales 
  conspicuous 
  Tetragonolepis 
  (p. 
  158). 
  

  

  Genus 
  ACENTROPHORUS, 
  Traquair. 
  

   [Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xxxiii. 
  1877, 
  p. 
  565.] 
  

  

  Trunk 
  fusiform. 
  Teeth 
  slender 
  ; 
  opercular 
  apparatus 
  well- 
  

   developed, 
  with 
  a 
  narrow 
  arched 
  preoperculum. 
  Pins 
  small, 
  with 
  

   very 
  large 
  fulcra 
  ; 
  dorsal 
  fin 
  short, 
  opposed 
  to 
  the 
  space 
  between 
  the 
  

   pelvic 
  pair 
  and 
  the 
  anal 
  ; 
  caudal 
  fin 
  symmetrical, 
  slightly 
  forked= 
  

   Scales 
  rhombic, 
  smooth 
  or 
  feebly 
  ornamented, 
  the 
  dorsal 
  ridge- 
  

   series 
  inconspicuous 
  ; 
  the 
  scales 
  of 
  the 
  flank 
  not 
  much 
  deeper 
  than 
  

   broad, 
  and 
  those 
  of 
  the 
  ventral 
  aspect 
  nearly 
  equilateral. 
  

  

  All 
  the 
  fishes 
  placed 
  here 
  were 
  originally 
  assigned 
  to 
  the 
  genus 
  

   Palceoniscus, 
  and 
  their 
  distinctness 
  was 
  first 
  pointed 
  out 
  by 
  C. 
  F. 
  

   Liitken, 
  Palseontogr. 
  vol. 
  xxii. 
  (1873), 
  p. 
  26, 
  footnote. 
  

  

  Acentrophorus 
  varians 
  (Kirkby). 
  

  

  1862. 
  Palceoniscus 
  varians, 
  J. 
  W. 
  Kirkby, 
  Ann. 
  Mag. 
  Nat. 
  Hist 
  [3] 
  

  

  vol. 
  ix. 
  p. 
  267. 
  

   1864. 
  Palceoniscus 
  varians, 
  J. 
  W. 
  Kirkby, 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  

  

  vol. 
  xx. 
  p. 
  353, 
  pi. 
  xviii. 
  fig. 
  2. 
  

   1877. 
  Acentrophorus 
  varians, 
  R. 
  H. 
  Traquair, 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  

  

  vol. 
  xxxiii. 
  p. 
  565. 
  

  

  e2 
  

  

  