﻿Report 
  of 
  the 
  State 
  Geologist. 
  

  

  1065 
  

  

  bilobed 
  at 
  its 
  summit. 
  Each 
  of 
  these 
  lobes 
  is 
  excavated 
  above 
  

   so 
  that 
  the 
  upper 
  portion 
  of 
  the 
  posterior 
  wall 
  is 
  free 
  from 
  the 
  

   rest 
  of 
  the 
  process. 
  In 
  front 
  of 
  this 
  is 
  a 
  broad, 
  smooth 
  floor, 
  

   sloping 
  toward 
  the 
  bottom 
  of 
  the 
  valve. 
  The 
  margins 
  of 
  this 
  area 
  

   form 
  the 
  elevated 
  socket-walls, 
  and 
  their 
  anterior 
  extremities^ 
  are 
  

   the 
  bases 
  of 
  the 
  crura. 
  The 
  dental 
  sockets 
  are 
  deep 
  and^their 
  

   outer 
  walls 
  corrugated 
  for 
  the 
  reception 
  of 
  the 
  teeth. 
  ^The 
  poste- 
  

   rior 
  portion 
  of 
  the 
  sockets 
  and 
  the 
  lower 
  part 
  of 
  the 
  cardinal 
  pro- 
  

   cess 
  are 
  covered 
  by 
  the 
  erect, 
  convex 
  chilidium. 
  At 
  the 
  anterior 
  

   edge 
  of 
  the 
  cardinal 
  process 
  lies 
  a 
  broad, 
  thick, 
  not 
  ] 
  elevated 
  

   median 
  ridge, 
  which 
  gradually 
  narrows 
  and 
  becomes 
  developed 
  

  

  Tropidoleptus 
  carinatus, 
  Conrad. 
  

  

  Fig. 
  514. 
  Tha 
  interior 
  of 
  the 
  brachial 
  valve 
  ; 
  showing 
  the 
  cardinal 
  process, 
  crenulated'dental 
  

  

  sockets, 
  loop 
  and 
  median 
  septum. 
  

   Fig. 
  515. 
  The 
  same 
  in 
  profile; 
  ; 
  showing 
  the 
  height 
  of 
  [the 
  [median 
  septum 
  and 
  the 
  mode 
  of 
  

  

  attachment 
  of 
  the 
  lamellae 
  of 
  the 
  loop. 
  

  

  into 
  a 
  sharp, 
  thin 
  septum, 
  attaining 
  its 
  highest 
  point 
  at 
  about 
  the 
  

   center 
  of 
  the 
  valve, 
  whence 
  it 
  slopes 
  rather 
  more 
  abruptly 
  down- 
  

   ward, 
  terminating 
  at 
  the 
  anterior 
  third 
  of 
  the 
  valve. 
  From 
  the 
  

   crural 
  bases 
  extends 
  a 
  pair 
  of 
  long, 
  slender 
  lamellar 
  processes, 
  

   which 
  curve 
  outward, 
  are 
  directed 
  upward, 
  again 
  converge 
  and 
  

   unite 
  with 
  the 
  median 
  septum 
  on 
  its 
  lateral 
  faces 
  and 
  just 
  in 
  front 
  

   of 
  its 
  highest 
  point. 
  Slightly 
  convergent, 
  slender 
  jugal 
  processes 
  

   are 
  given 
  off 
  not 
  far 
  from 
  the 
  origin 
  of 
  the 
  lateral 
  lamellae. 
  The 
  

   scars 
  of 
  the 
  adductor 
  muscles 
  are 
  situated 
  just 
  in 
  front 
  of 
  the 
  

   cardinal 
  process 
  on 
  either 
  side 
  of 
  the 
  septum, 
  and 
  are 
  not 
  clearly 
  

   delimited. 
  

  

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