﻿The 
  Fauna 
  of 
  the 
  Niagara 
  Group. 
  193 
  

  

  These 
  extravagant 
  forms 
  of 
  Dalmanites 
  or 
  Od 
  otoceph- 
  

   alus, 
  in 
  the 
  last 
  two 
  geological 
  stages, 
  are 
  associated 
  with 
  

   the 
  staid 
  and 
  almost 
  unvarying 
  Phacops 
  which 
  begins 
  and 
  

   ends 
  its 
  existence 
  in 
  the 
  "three 
  latest 
  named 
  geological 
  

   periods. 
  * 
  * 
  * 
  

  

  For 
  the 
  present 
  I 
  propose 
  to 
  recognize 
  the 
  following 
  species 
  

   as 
  Dalmanites, 
  until 
  it 
  shall 
  be 
  determined 
  whether 
  the 
  

   forms 
  possessing 
  the 
  characters 
  of 
  the 
  genus 
  Odontocepha- 
  

   lus 
  may 
  be 
  properly 
  distinguishable 
  as 
  a 
  separate 
  group. 
  

  

  Dalmanites 
  vigilans. 
  

  

  Plate 
  33, 
  Figs. 
  1-4. 
  

  

  Dalmanites 
  vigilans 
  Hall. 
  Rep. 
  Prog. 
  G-eol. 
  Surv. 
  Wis., 
  p. 
  57. 
  1861. 
  

  

  Dalmania 
  vigilans 
  Hall. 
  20th 
  Rep. 
  St. 
  Cab. 
  Nat. 
  Hist., 
  p. 
  335, 
  pi. 
  21, 
  figs. 
  16-18. 
  

   Rev. 
  Edit., 
  p. 
  426. 
  

  

  Dalmania 
  vigilans 
  Hall. 
  Doc. 
  Edit. 
  28th 
  Rep. 
  St. 
  Mus. 
  Nat. 
  Hist. 
  Explana- 
  

   tion 
  of 
  pi. 
  33, 
  figs. 
  1-4. 
  1876. 
  

  

  General 
  form 
  of 
  body 
  broadly 
  ovate, 
  greatest 
  breadth 
  across 
  

   the 
  posterior 
  part 
  of 
  the 
  cephalic 
  shield. 
  

  

  Head 
  convex, 
  semi-elliptical, 
  breadth 
  about 
  twice 
  as 
  great 
  

   as 
  the 
  length 
  (exclusive 
  of 
  the 
  frontal 
  projection) 
  ; 
  border 
  ex- 
  

   tended 
  in 
  front 
  into 
  a 
  triangular, 
  sometimes 
  truncate, 
  process, 
  

   the 
  base 
  of 
  which 
  is 
  little 
  less 
  than 
  one-half 
  as 
  wide 
  as 
  the 
  

   width 
  of 
  the 
  anterior 
  portion 
  of 
  the 
  glabella 
  ; 
  in 
  older 
  indi- 
  

   viduals 
  this 
  projection 
  becomes 
  more 
  obtuse 
  and 
  sometimes 
  

   rounded 
  ; 
  lateral 
  borders 
  broad, 
  flattened, 
  separated 
  from 
  the 
  

   cheeks 
  by 
  a 
  distinct 
  groove, 
  produced 
  posteriorly 
  into 
  long, 
  

   slender 
  parallel 
  spines, 
  which 
  do 
  not 
  extend 
  beyond 
  the 
  gen- 
  

   eral 
  outline, 
  and 
  are 
  continued 
  as 
  far 
  as 
  the 
  extremities 
  of 
  the 
  

   fifth 
  thoracic 
  segment. 
  Glabella 
  large, 
  depressed-convex, 
  wid- 
  

   ening 
  in 
  front 
  to 
  twice 
  its 
  width 
  at 
  the 
  posterior 
  margin, 
  divided 
  

   into 
  lobes 
  by 
  three 
  pairs 
  of 
  transverse 
  furrows 
  exclusive 
  of 
  

   the 
  occipital 
  furrow, 
  which 
  is 
  distinct 
  and 
  continuous 
  ; 
  the 
  

   two 
  posterior 
  furrows 
  distinct 
  at 
  the 
  sides, 
  but 
  not 
  extending 
  

   entirely 
  across 
  the 
  glabella 
  except 
  in 
  a 
  faint 
  depression 
  ; 
  the 
  

   anterior 
  furrows 
  deep, 
  very 
  distinct, 
  situated 
  a 
  little 
  ante- 
  

   rior 
  to 
  the 
  eyes, 
  extending 
  each 
  about 
  one-third 
  across 
  the 
  

   glabella 
  and 
  giving 
  to 
  the 
  frontal 
  lobe 
  a 
  transversely 
  ellipti- 
  

   cal 
  outline 
  ; 
  occipital 
  ring 
  narrow, 
  ornamented 
  in 
  the 
  middle 
  

   by 
  a 
  single, 
  short, 
  sharp 
  spine. 
  Eyes 
  very 
  prominent, 
  short 
  

   reniform, 
  containing 
  about 
  thirty 
  -five 
  vertical 
  ranges 
  of 
  lenses, 
  

   19 
  

  

  