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  E. 
  RAY 
  LANKESTEE. 
  

  

  somites 
  may 
  be 
  more 
  or 
  less 
  than 
  eighteen; 
  and 
  may 
  bo 
  

   grouped 
  only 
  as 
  head 
  (prosoma) 
  and 
  trunk, 
  or 
  maybe 
  further 
  

   differentiated. 
  A 
  telsonic 
  tergal 
  shield 
  of 
  greater 
  or 
  less 
  

   size 
  is 
  always 
  present, 
  which 
  may 
  be 
  imperfectly 
  divided 
  into 
  

   well-marked 
  but 
  immovable 
  tergites 
  indicating 
  incompletely 
  

  

  Fig. 
  34. 
  — 
  Restoration 
  of 
  Triastliriis 
  Becki, 
  Green, 
  as 
  deter- 
  

   mined 
  by 
  Mr. 
  Beeclier 
  from 
  specimens 
  obtained 
  from 
  the 
  Utica 
  Slates 
  

   (Ordovician), 
  New 
  York. 
  A, 
  dorsal; 
  B, 
  ventral 
  snrface. 
  In 
  the 
  

   latter 
  the 
  single 
  pair 
  of 
  antennse 
  springing 
  up 
  from 
  each 
  side 
  of 
  the 
  

   canierostome 
  or 
  hypostome 
  or 
  upper 
  lip-lobe 
  are 
  seen. 
  Four 
  pairs 
  

   of 
  appendages 
  besides 
  these 
  are 
  seen 
  to 
  belong 
  to 
  the 
  cephalic 
  

   tergum. 
  All 
  the 
  appendages 
  are 
  pediform 
  and 
  biramose 
  ; 
  all 
  have 
  

   a 
  prominent 
  gnathobase, 
  and 
  in 
  all 
  the 
  exopodite 
  carries 
  a 
  comb-like 
  

   series 
  of 
  secondary 
  processes. 
  (After 
  Beecher, 
  from 
  Zittel.) 
  

  

  differentiated 
  somites. 
  The 
  single 
  pair 
  of 
  palpiform 
  appen- 
  

   dages 
  in 
  front 
  of 
  the 
  mouth 
  has 
  been 
  found 
  in 
  one 
  instance 
  to 
  

   be 
  antenniform, 
  whilst 
  the 
  numerous 
  post-oral 
  appendages 
  in 
  

  

  