﻿MACK0SEMIID2E. 
  181 
  

  

  p. 
  166), 
  described 
  and 
  figured 
  by 
  the 
  present 
  writer 
  in 
  

   Proc. 
  Geol. 
  Assoc, 
  vol. 
  xi. 
  (1890), 
  p. 
  293, 
  pi. 
  iii. 
  fig. 
  9 
  ; 
  

   Stonesfield 
  Slate, 
  Stonesfield. 
  Enniskillen 
  Coll. 
  

  

  P. 
  957. 
  Left 
  dentary 
  with 
  eight 
  teeth, 
  probably 
  of 
  the 
  same 
  species 
  ; 
  

   Stonesfield. 
  Egerton 
  Coll. 
  

  

  The 
  following 
  species 
  is 
  only 
  imperfectly 
  defined 
  and 
  is 
  not 
  

   represented 
  in 
  the 
  Collection 
  : 
  — 
  

  

  Macrosemius 
  helence, 
  V. 
  Thiolliere, 
  Ann. 
  Soc. 
  Sci. 
  Phys. 
  & 
  Nat. 
  

   Lyon, 
  [2] 
  vol. 
  iii. 
  (1850), 
  p. 
  135, 
  and 
  Poiss. 
  Foss. 
  Bugey, 
  

   pt. 
  ii. 
  (1873), 
  p. 
  14, 
  pi. 
  vi. 
  fig. 
  2 
  ; 
  H. 
  E. 
  Sauvage, 
  

   Bull. 
  Soc. 
  Geol. 
  France, 
  [3] 
  vol. 
  xi. 
  (1883), 
  p. 
  478.— 
  

   Lower 
  Kimmeridgian 
  (Lithographic 
  Stone); 
  Cirin, 
  Ain, 
  

   France. 
  [Imperfect 
  small 
  fish 
  ; 
  Lyons 
  Museum.] 
  

  

  Genus 
  PETALOPTERYX, 
  Pictet. 
  

   [Poiss. 
  Foss. 
  Mt. 
  Liban, 
  1850, 
  p. 
  20.] 
  

  

  Syn. 
  Aphanepygus, 
  F. 
  Bassani, 
  Verhandl. 
  k. 
  k. 
  geol. 
  Reichsanst. 
  1879, 
  

   p. 
  162. 
  

  

  Trunk 
  much 
  elongated, 
  gradually 
  tapering 
  from 
  the 
  occiput 
  

   backwards; 
  head 
  small, 
  snout 
  acute. 
  Teeth 
  much 
  elongated, 
  

   closely 
  arranged 
  ; 
  suborbital 
  plates 
  subdivided 
  into 
  numerous 
  small 
  

   tesserge. 
  Fulcra 
  absent, 
  except 
  on 
  the 
  caudal 
  fin; 
  pectoral 
  fins 
  

   much 
  enlarged 
  ; 
  dorsal 
  fin 
  consisting 
  of 
  unbranched 
  rays, 
  arising 
  

   shortly 
  behind 
  the 
  occiput 
  and 
  extending 
  continuously 
  to 
  the 
  

   caudal 
  pedicle 
  ; 
  [anal 
  fin 
  apparently 
  absent 
  ; 
  caudal 
  fin 
  scarcely 
  if 
  

   at 
  all 
  forked]. 
  Squamation 
  robust 
  and 
  extending 
  over 
  the 
  whole 
  

   trunk, 
  the 
  flank-scales 
  not 
  much 
  (if 
  at 
  all), 
  deepened, 
  but 
  all 
  more 
  

   or 
  less 
  irregular, 
  and 
  the 
  vertical 
  series 
  apparently 
  sometimes 
  

   dichotomous 
  dorsally 
  and 
  ventrally. 
  

  

  Petalopteryx 
  syriacus, 
  Pictet. 
  

  

  1850. 
  Petalopteryx 
  syriacus, 
  F. 
  J. 
  Pictet, 
  Poiss. 
  Foss. 
  Mt. 
  Liban, 
  p. 
  22, 
  

  

  pi. 
  iii. 
  fig. 
  1 
  . 
  

   1866. 
  Petalopteryx 
  syriacus, 
  F. 
  J. 
  Pictet 
  & 
  A. 
  Humbert, 
  Nouv. 
  Rech. 
  

  

  Poiss. 
  Foss. 
  Mt. 
  Liban, 
  p. 
  54. 
  

   1882. 
  Petalopteryx 
  syriacus, 
  F. 
  Bassani, 
  Denkschr. 
  k. 
  Akad. 
  Wiss., 
  

  

  math.-naturw. 
  CI. 
  vol. 
  xlv. 
  p. 
  268. 
  

  

  Type. 
  Nearly 
  complete 
  fish 
  ; 
  Geneva 
  Museum. 
  

   The 
  type 
  species, 
  attaining 
  a 
  length 
  of 
  about 
  0*16. 
  Maximum 
  

   depth 
  of 
  trunk 
  contained 
  nearly 
  four-and-a-half 
  times 
  in 
  its 
  length 
  

  

  