﻿182 
  

  

  COLPOCERAS 
  VIRGATUM. 
  

   Plate 
  5, 
  fig. 
  2. 
  

  

  Tube 
  virgate, 
  scarcely 
  diminishing 
  towards 
  the 
  apex 
  ; 
  surface 
  strong- 
  

   ly 
  annulated 
  ; 
  annulations 
  arching 
  towards 
  the 
  apex 
  on 
  the 
  back 
  of 
  the 
  

   shell 
  and 
  bending 
  downwards 
  in 
  an 
  abrupt 
  sinus 
  on 
  the 
  ventral 
  side, 
  

   and 
  becoming 
  almost 
  entirely 
  lost 
  on 
  the 
  ventral 
  line 
  ; 
  septa 
  following 
  

   the 
  direction 
  of 
  the 
  annulations 
  and 
  arranged 
  between 
  them, 
  except 
  on 
  

   the 
  ventral 
  side 
  where 
  they 
  encroach 
  a 
  little 
  upon 
  the 
  annulation, 
  being 
  

   more 
  abruptly 
  bent 
  downwards 
  ; 
  septa 
  in 
  the 
  longitudinal 
  section, 
  cut- 
  

   ting 
  each 
  side, 
  regularly 
  arched 
  ; 
  section 
  when 
  not 
  compressed 
  cylin- 
  

   drical 
  ; 
  siphuncle 
  unknown 
  ; 
  character 
  of 
  the 
  surface, 
  except 
  the 
  annu- 
  

   lations, 
  unknown. 
  

  

  This 
  species 
  occurs 
  near 
  the 
  junction 
  of 
  the 
  Birdseye 
  and 
  Black 
  river 
  

   limestones 
  in 
  Lewis 
  county. 
  

  

  ASAPHUS 
  EXTANS. 
  

   Plate 
  3, 
  fig. 
  1. 
  

  

  Reference. 
  — 
  Asaphus 
  extans. 
  Palaeontology 
  of 
  New- 
  York, 
  vol. 
  i., 
  

   page 
  228, 
  plate 
  60, 
  fig. 
  .2, 
  a, 
  b, 
  c. 
  

  

  This 
  species, 
  which 
  was 
  described 
  as 
  an 
  asaphus, 
  with 
  some 
  doubt, 
  

   has 
  again 
  fallen 
  under 
  my 
  observation, 
  and 
  though 
  the 
  specimens 
  yet 
  

   procured 
  are 
  fragments, 
  they 
  throw 
  some 
  farther 
  light 
  upon 
  the 
  char- 
  

   acter 
  of 
  4he 
  fossil. 
  These 
  specimens 
  are 
  mostly 
  in 
  a 
  bad 
  state 
  of 
  pre- 
  

   servation, 
  from 
  a 
  dark 
  shaly 
  layer 
  near 
  the 
  base 
  of 
  the 
  Trenton 
  lime- 
  

   stone 
  in 
  Lowville. 
  The 
  character 
  of 
  the 
  caudal 
  shield 
  which 
  is 
  preser- 
  

   ved 
  in 
  several 
  specimens 
  is 
  well 
  marked, 
  though 
  the 
  rings 
  of 
  the 
  thorax 
  

   attached 
  are 
  so 
  much 
  obliterated 
  as 
  to 
  afford 
  very 
  little 
  satisfactory 
  evi- 
  

   dence 
  of 
  their 
  number 
  or 
  character. 
  Still 
  there 
  appears 
  to 
  be 
  nine 
  or 
  

   ten 
  articulations 
  of 
  the 
  thorax, 
  though 
  the 
  junction 
  with 
  the 
  caudal 
  

   shield 
  is 
  obscure. 
  

  

  In 
  connexion 
  with 
  a 
  mutilated 
  specimen, 
  we 
  have 
  the 
  convex 
  middle 
  

   lobe 
  of 
  the 
  cephalic 
  shield, 
  with 
  two 
  large 
  and 
  prominent 
  eyes. 
  This 
  

   specimen 
  does 
  not 
  preserve 
  the 
  margin 
  of 
  the 
  shield, 
  but 
  in 
  another 
  one 
  

   we 
  find 
  the 
  two 
  lateral 
  portions 
  of 
  the 
  shield 
  preserved 
  in 
  their 
  natural 
  

   relations 
  to 
  each 
  other, 
  the 
  central 
  lobe 
  being 
  wanting. 
  This 
  fragment 
  

   proves 
  that 
  the 
  facial 
  suture 
  terminated 
  on 
  the 
  base 
  of 
  the 
  shield 
  as 
  in 
  

   asaphus, 
  though 
  it 
  is 
  difficult 
  to 
  reconcile 
  the 
  number 
  of 
  articulations 
  of 
  

   the 
  thorax 
  with 
  that 
  genus. 
  The 
  prominent 
  eyes 
  are 
  also 
  like 
  asaphus, 
  

   the 
  form 
  of 
  the 
  head 
  is 
  rather 
  more 
  prominent 
  in 
  the 
  middle 
  lobe 
  than 
  

  

  