﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  221 
  

  

  gciicl 
  Spines. 
  The 
  compound 
  eyes 
  are 
  situated 
  on 
  the 
  free 
  cheeks, 
  

   and 
  they 
  are 
  overshadowed 
  by 
  more 
  or 
  less 
  prominent 
  eyehds 
  or 
  

   palpebral 
  lobes, 
  which 
  are 
  lateral 
  lobes 
  from 
  the 
  fixed 
  cheeks. 
  The 
  

   facial 
  suture 
  thus 
  passes 
  between 
  the 
  eyes 
  and 
  the 
  palpebral 
  lobes, 
  

   and 
  when, 
  as 
  is 
  often 
  the 
  case, 
  the 
  free 
  cheeks 
  become 
  separated 
  

   after 
  the 
  death 
  of 
  the 
  animal, 
  only 
  the 
  palpebral 
  lobes 
  remain 
  on 
  the 
  

   central 
  portion 
  of 
  the 
  cephalon. 
  The 
  border 
  of 
  the 
  cephalon 
  is 
  

   often 
  distinctly 
  marked, 
  and 
  is 
  spoken 
  of 
  as 
  the 
  cephalic 
  limb. 
  At 
  the 
  

   margin 
  it 
  is 
  folded 
  down 
  and 
  under, 
  making 
  the 
  doublure, 
  which, 
  

   continued 
  backward, 
  often 
  produces 
  hollow 
  or 
  solid 
  genal 
  spines. 
  

   Near 
  the 
  anterior 
  lower 
  portion 
  of 
  the 
  doublure 
  lies 
  the 
  lower 
  lip, 
  

   or 
  hypostoma, 
  which 
  is 
  usually 
  found 
  separate. 
  

  

  The 
  thorax 
  consists 
  of 
  a 
  varying 
  number 
  of 
  segments 
  or 
  rings, 
  

   articulated 
  with 
  each 
  other, 
  and 
  commonly 
  permitting 
  enrolment. 
  

   Each 
  consists 
  of 
  a 
  central 
  anniilus 
  and 
  lateral 
  pleurae. 
  

  

  The 
  tail, 
  or 
  pygidium, 
  consists 
  of 
  a 
  single 
  piece, 
  comprising 
  a 
  cen- 
  

   tral 
  axis 
  and 
  lateral 
  lobes. 
  The 
  axis 
  and 
  the 
  lobes 
  commonly 
  show 
  

   transverse 
  furrows, 
  corresponding 
  to 
  the 
  divisions 
  of 
  the 
  thorax, 
  and 
  

   they 
  are 
  often 
  so 
  strongly 
  marked 
  that 
  a 
  line 
  of 
  division 
  between 
  

   thorax 
  and 
  pygidium 
  is 
  difficult 
  to 
  determine. 
  

  

  Great 
  advances 
  have 
  recently 
  been 
  made 
  in 
  our 
  knowledge 
  of 
  the 
  

   ventral 
  side 
  of 
  trilobites. 
  Probably 
  all 
  of 
  them 
  had 
  jointed 
  appen- 
  

   dages, 
  which 
  included 
  antennae, 
  mouth 
  parts 
  and 
  legs, 
  comparable 
  

   in 
  a 
  general 
  way 
  to 
  those 
  of 
  modern 
  Crustacea. 
  

  

  Genus 
  homalonotus 
  Koenig 
  

  

  [Ety.: 
  otjAl/Mi, 
  on 
  the 
  same 
  level; 
  vihzo^, 
  back] 
  

  

  (1825. 
  hones 
  foss. 
  sec 
  tiles, 
  p. 
  4) 
  

  

  Body 
  usually 
  large, 
  depressed 
  above, 
  with 
  abruptly 
  sloping 
  sides. 
  

   The 
  axial 
  furrows 
  are 
  indistinct 
  or 
  obsolete. 
  Cephalon 
  depressed 
  

   convex, 
  wider 
  than 
  long, 
  with 
  rounded 
  genal 
  angles, 
  and 
  somewhat 
  

   produced 
  anterior 
  margin; 
  glabella 
  almost 
  rectangular, 
  smooth, 
  or 
  

   with 
  faint 
  lateral 
  furrows. 
  Small 
  eyes 
  situated 
  behind 
  the 
  middle, 
  

   and 
  converging 
  facial 
  sutures 
  are 
  characteristic. 
  Thorax 
  of 
  13 
  

   deeply 
  grooved 
  segments. 
  Pygidium 
  smaller 
  than 
  the 
  cephalon, 
  

   elongate 
  triangular, 
  rounded 
  or 
  produced 
  posteriorly; 
  axis 
  wath 
  10 
  

   to 
  14 
  annulations; 
  lateral 
  lobes 
  smooth 
  or 
  with 
  posteriorly 
  sloping 
  

   ribs. 
  

  

  Homalonotus 
  delphinocephalus 
  (Green) 
  (Fig. 
  153) 
  (Hall. 
  1852. 
  

   Pal. 
  N. 
  7.2:309, 
  pi. 
  68) 
  

  

  Distinguishing 
  characters. 
  Subtriangular 
  cephalon; 
  subquadrate 
  

   glabella, 
  widening 
  a 
  little 
  posteriorly; 
  small 
  lateral 
  eyes; 
  acute 
  anter- 
  

   ior 
  termination 
  of 
  cephalon; 
  non-trilobate 
  character 
  of 
  thorax, 
  nar- 
  

   rowing 
  rapidly 
  toward 
  the 
  posterior 
  end 
  ; 
  abruptly 
  triangular 
  pygid- 
  

  

  