﻿Report 
  of 
  the 
  State 
  Geologist. 
  

  

  1099 
  

  

  and 
  divaricator 
  muscles, 
  and 
  probably 
  rests 
  upon 
  the 
  bottom 
  of 
  

   the 
  valve 
  and 
  is 
  not 
  vaulted. 
  

  

  In 
  the 
  brachial 
  valve 
  there 
  is 
  a 
  prominent 
  cardinal 
  process 
  

   from 
  the 
  base 
  of 
  which 
  diverge 
  two 
  lateral 
  ridge 
  or 
  socket 
  walls, 
  

   lying 
  just 
  within 
  the 
  hinge-line 
  : 
  behind 
  them 
  are 
  linear 
  depres- 
  

   sions 
  or 
  dental 
  sockets. 
  There 
  is 
  also 
  a 
  low 
  median 
  ridge 
  extend- 
  

   ing 
  from 
  the 
  base 
  of 
  the 
  cardinal 
  process 
  into 
  the 
  pailial 
  region. 
  

  

  The 
  substance 
  of 
  the 
  shell 
  shows 
  a 
  coarsely 
  prismatic 
  cellular 
  

   structure, 
  as 
  in 
  Poramboxites 
  and 
  Eichwaldia. 
  According 
  to 
  

   Barrois. 
  this 
  cellular 
  lamina 
  is 
  not 
  superficial 
  but 
  is 
  covered 
  by 
  

   a 
  thin 
  epidermal 
  layer. 
  

  

  Type, 
  Aulcoryhynch 
  us 
  PacAti, 
  Dittmar. 
  Carboniferous 
  limestone. 
  

  

  Distribution. 
  Carboniferous. 
  

  

  Richthofenia, 
  Kayser. 
  1S81. 
  

   These 
  peculiar 
  fossils, 
  which 
  bear 
  a 
  striking 
  external 
  resem- 
  

   blance 
  to 
  certain 
  operculated 
  corals, 
  and 
  present 
  some 
  suggestive 
  

  

  Fig. 
  6€S. 
  

  

  SSS^^^v 
  Wi% 
  

  

  Fig. 
  666. 
  

  

  Fig. 
  

  

  Fig. 
  669. 
  

  

  Richthofenia 
  Laicrenciana, 
  de 
  Koninck. 
  

   Fig. 
  666. 
  The 
  exterior 
  of 
  the 
  two 
  valves 
  in 
  articulation. 
  

   Fig 
  657. 
  Longitudinal 
  section 
  of 
  the 
  pedicle-valve; 
  showing 
  the 
  interior 
  cavity 
  and 
  the 
  cellular 
  

  

  shell 
  substance. 
  

   Fig. 
  668. 
  The 
  interior 
  of 
  the 
  pedicle- 
  valve 
  : 
  showing 
  the 
  hinge-line 
  and 
  muscular 
  scars. 
  

   Fig. 
  669. 
  The 
  interior 
  of 
  the 
  brachial 
  valve. 
  (Waagex.) 
  

  

  similarities 
  to 
  the 
  lamellibranchs 
  Hippurites 
  and 
  Eadiolites, 
  

   have 
  been 
  carefully 
  elaborated 
  by 
  Waagex, 
  who 
  arrives 
  at 
  the 
  

  

  157 
  

  

  