﻿Report 
  of 
  the 
  State 
  Geologist. 
  1031 
  

  

  which 
  converge 
  and 
  unite 
  before 
  reaching 
  the 
  bottom 
  of 
  the 
  

   valve. 
  Thus 
  is 
  formed 
  a 
  deep 
  but 
  short 
  spondylium, 
  which 
  is 
  

   supported, 
  near 
  its 
  apical 
  portion, 
  by 
  a 
  median 
  septum, 
  but 
  is 
  

   free 
  for 
  fully 
  one-half 
  its 
  length. 
  

  

  In 
  the 
  brachial 
  valve 
  there 
  are 
  also 
  two 
  convergent 
  plates 
  

   bounding 
  the 
  deltidial 
  cavity, 
  larger 
  and 
  stronger 
  than 
  those 
  of 
  

   the 
  opposite 
  valve. 
  These 
  plates 
  may 
  rest 
  upon 
  the 
  bottom 
  of 
  

   the 
  valve, 
  and, 
  toward 
  the 
  posterior 
  extremity, 
  probably 
  always 
  

   do, 
  but 
  anteriorly 
  they 
  become 
  free, 
  forming 
  a 
  spondylium 
  

   which 
  is 
  supported 
  by 
  a 
  median 
  septum 
  extending 
  beyond 
  the 
  

   anterior 
  edge 
  of 
  the 
  plate. 
  Thus 
  these 
  two 
  valves, 
  which 
  are 
  

   very 
  similar 
  in 
  exterior, 
  the 
  pedicle-valve 
  being 
  only 
  slightly 
  the 
  

   more 
  convex 
  and 
  with 
  a 
  low 
  median 
  sinus, 
  are 
  also 
  closely 
  alike 
  

   on 
  the 
  interior, 
  each 
  being 
  furnished 
  with 
  a 
  spondylium. 
  

  

  Type, 
  Syntrophia 
  lateralis, 
  Whitfield 
  (sp.). 
  

  

  Distribution. 
  Cambrian 
  (?) 
  — 
  Lower 
  Silurian. 
  

  

  Camarophoria, 
  King. 
  1846. 
  

   (Plate 
  45, 
  figs. 
  5, 
  6.) 
  

  

  Subtrigonal, 
  concavo-convex 
  rhynchonelliform 
  shells, 
  with 
  

   median 
  fold 
  and 
  sinus 
  well 
  developed, 
  and 
  surface 
  more 
  or 
  less 
  

   strongly 
  plicated. 
  Beak 
  sharp, 
  incurved 
  ; 
  deltidial 
  plates 
  in 
  an 
  

   incipient 
  condition, 
  often 
  wanting. 
  

  

  In 
  the 
  pedicle-valve 
  the 
  dental 
  plates 
  converge, 
  forming 
  a 
  

   moderately 
  large 
  spondylium 
  which, 
  in 
  the 
  umbonai 
  region, 
  rests 
  

   upon 
  the 
  bottom 
  of 
  the 
  valve, 
  but 
  anteriorly 
  is 
  supported 
  by 
  a 
  

   vertical 
  median 
  septum. 
  The 
  spondylium 
  is 
  short, 
  while 
  the 
  

   supporting 
  septum 
  is 
  carried 
  beyond 
  it, 
  sometimes 
  to 
  nearly 
  one- 
  

   half 
  the 
  length 
  of 
  the 
  shell. 
  Near 
  the 
  teeth, 
  which 
  are 
  small, 
  

   there 
  are 
  two 
  accessory 
  supporting 
  lamellae 
  abutting 
  on 
  one 
  side 
  

   against 
  the 
  outer 
  surface 
  of 
  the 
  converging 
  dental 
  plates, 
  and 
  on 
  

   the 
  other 
  against 
  the 
  interior 
  cardinal 
  surface 
  of 
  the 
  valve 
  ; 
  

   thus 
  inclosing 
  small 
  lateral 
  umbonai 
  cavities. 
  Muscular 
  scars 
  of 
  

   this 
  valve 
  always 
  obscure. 
  

  

  In 
  the 
  brachial 
  valve 
  the 
  cardinal 
  plate 
  is 
  narrow, 
  sub 
  triangular, 
  

   in 
  the 
  typical 
  species 
  bearing 
  a 
  very 
  small 
  cardinal 
  process, 
  

   which 
  in 
  other 
  species 
  is 
  rarely 
  present. 
  The 
  hinge-plate 
  is 
  

   traversed 
  by 
  two 
  fine 
  divergent 
  ridges 
  running 
  outward 
  from 
  

  

  