﻿196 
  Twenty-eighth 
  Eepokt 
  ox 
  the 
  State 
  Museum. 
  

  

  gradually 
  decrease 
  in 
  size 
  posteriorly, 
  and 
  terminate 
  in 
  a 
  

   slender 
  spine 
  about 
  half 
  as 
  long 
  as 
  the 
  caudal 
  plate. 
  The 
  

   lateral 
  lobe 
  has 
  ten 
  articulations, 
  eight 
  of 
  which 
  are 
  divided 
  

   by 
  a 
  longitudinal 
  furrow 
  ; 
  the 
  last 
  two 
  are 
  simple, 
  and 
  all 
  be- 
  

   come 
  obsolete 
  just 
  within 
  the 
  margin. 
  

  

  Surface 
  of 
  the 
  head, 
  except 
  the 
  anterior 
  and 
  lateral 
  borders, 
  

   covered 
  with 
  small, 
  somewhat 
  pointed 
  pustules, 
  the 
  border 
  

   having 
  only 
  a 
  finely 
  granulose 
  texture. 
  Occipital 
  and 
  axial 
  

   rings 
  of 
  the 
  thorax 
  and 
  pygidium 
  each 
  marked 
  with 
  seven 
  

   small 
  spiniform 
  pustules, 
  the 
  central 
  one 
  the 
  longest 
  ; 
  those 
  

   of 
  the 
  pygidium 
  become 
  closely 
  crowded 
  in 
  the 
  posterior 
  por- 
  

   tion 
  ; 
  there 
  are 
  sometimes 
  two 
  or 
  more 
  additional 
  smaller 
  

   pustules 
  on 
  the 
  stronger 
  rings 
  of 
  the 
  thorax. 
  

  

  Length 
  of 
  a 
  medium-sized 
  specimen 
  (exclusive 
  of 
  the 
  cau- 
  

   dal 
  spine) 
  80 
  mm. 
  ; 
  greatest 
  width 
  of 
  the 
  head 
  somewhat 
  more 
  

   than 
  50 
  mm. 
  ; 
  length 
  of 
  the 
  head 
  from 
  the 
  occipital 
  ring 
  15 
  

   mm. 
  ; 
  greatest 
  width 
  of 
  thorax 
  48 
  mm. 
  ; 
  width 
  of 
  axial 
  lobe 
  

   13 
  mm. 
  ; 
  length 
  of 
  pygidium 
  (exclusive 
  of 
  the 
  spine) 
  28 
  mm. 
  ; 
  

   greatest 
  width 
  of 
  pygidium 
  48 
  mm. 
  Some 
  of 
  the 
  large 
  ceph- 
  

   alic 
  shields 
  have 
  a 
  width 
  of 
  from 
  80 
  to 
  100 
  mm. 
  

  

  The 
  heads 
  of 
  this 
  species, 
  in 
  a 
  tolerably 
  good 
  state 
  of 
  pre- 
  

   servation, 
  are 
  very 
  common 
  ; 
  the 
  remainder 
  of 
  the 
  body 
  being 
  

   mostly 
  found 
  in 
  a 
  fragmentary 
  condition. 
  

  

  Dalmanites 
  bicoknis. 
  

  

  Plate 
  33, 
  Fig. 
  18. 
  

  

  Dalmania 
  bicornis 
  Hall. 
  Doc. 
  Edit. 
  28th 
  Rept. 
  St. 
  Mus. 
  Nat. 
  Hist. 
  Expla- 
  

   nation 
  of 
  pi. 
  33, 
  fig. 
  18. 
  1876. 
  

  

  This 
  species 
  is 
  indicated 
  from 
  the 
  occurrence 
  of 
  an 
  incom- 
  

   plete 
  border 
  of 
  the 
  buckler, 
  which 
  preserves 
  a 
  strong 
  bifurcat- 
  

   ory 
  anterior 
  process 
  — 
  a 
  feature 
  sufficiently 
  characteristic 
  to 
  

   distinguish 
  it 
  from 
  any 
  trilobite 
  of 
  the 
  Niagara 
  formation 
  

   yet 
  known 
  to 
  us. 
  The 
  form 
  bears 
  much 
  general 
  resem- 
  

   blance 
  to 
  D. 
  nasutus 
  of 
  the 
  Lower 
  Helderberg 
  formation, 
  

   which 
  has 
  a 
  much 
  larger 
  bifurcating 
  anterior 
  process, 
  and 
  in 
  

   which 
  the 
  anterior 
  lobe 
  of 
  the 
  glabella 
  is 
  projected 
  forward 
  

   beyond 
  the 
  line 
  of 
  general 
  contour 
  of 
  the 
  cephalic 
  shield. 
  

  

  