﻿Report 
  of 
  the 
  State 
  Geologist, 
  1025 
  

  

  are 
  obliquely 
  concave, 
  the 
  outer 
  and 
  anterior 
  angle 
  being 
  much 
  

   elevated 
  and 
  the 
  slope 
  thence 
  to 
  the 
  dental 
  sockets 
  abrupt. 
  The 
  

   crura 
  are 
  attached 
  to 
  the 
  inner 
  margins 
  of 
  these 
  plates, 
  are 
  not 
  

   curved, 
  but 
  their 
  distal 
  extremities 
  are 
  expanded 
  into 
  spoon- 
  

   shaped 
  processes 
  which 
  have 
  their 
  concave 
  surfaces 
  toward 
  the 
  

   brachial 
  valve. 
  There 
  are 
  no 
  thickened 
  muscular 
  scars 
  as 
  in 
  the 
  

   opposite 
  valve. 
  

  

  The 
  surface 
  is 
  covered 
  with 
  sharply 
  angular, 
  simple 
  plications, 
  

   most 
  of 
  which 
  begin 
  in 
  the 
  umbonal 
  regions, 
  and 
  the 
  broad 
  fold 
  

   and 
  sinus 
  may 
  bear 
  as 
  many 
  as 
  from 
  eight 
  to 
  twelve 
  of 
  these. 
  

   All 
  the 
  plications 
  are 
  crossed 
  by 
  fine, 
  sharp 
  concentric 
  lines 
  of 
  

   ornamentation, 
  which 
  crenulate 
  the 
  summits 
  of 
  the 
  ridges. 
  

  

  Shell-substance 
  fibrous, 
  impunctate. 
  

  

  Type, 
  Cyclorhina 
  nobilis, 
  Hall. 
  

  

  Distribution. 
  Middle 
  Devonian. 
  

  

  Terebratuloidea, 
  Waagen. 
  1883. 
  

  

  Shells 
  oval 
  or 
  rounded, 
  with 
  strongly 
  plicated 
  valves 
  and 
  a 
  

   high 
  median 
  fold 
  in 
  the 
  brachial, 
  and 
  a 
  corresponding 
  sinus 
  in 
  the 
  

   pedicle-valve. 
  Beak 
  truncated 
  with 
  a 
  terminal 
  round 
  foramen 
  ; 
  

   deltidial 
  plates 
  distinct. 
  

  

  Teeth 
  strong, 
  not 
  supported 
  by 
  dental 
  plates. 
  Brachial 
  valve 
  

   with 
  a 
  tolerably 
  large 
  triangular 
  hinge-plate, 
  which 
  is 
  triangularly 
  

  

  Fig. 
  415. 
  Fig. 
  4j6. 
  Fig. 
  417. 
  

  

  Terebratuloidea 
  Davidsoni, 
  Waagen. 
  

   Fig. 
  415.— 
  View 
  of 
  the 
  exterior. 
  

   Fig. 
  416.— 
  Interior 
  of 
  the 
  pedicle- 
  valve. 
  

   Fig. 
  417.— 
  Interior 
  of 
  the 
  brachial 
  valve. 
  (Waagen.) 
  

  

  divided. 
  There 
  is 
  no 
  cardinal 
  process. 
  On 
  both 
  sides 
  of 
  the 
  

   median 
  incision 
  very 
  short 
  curved 
  crura 
  take 
  their 
  origin, 
  and 
  

   proceed 
  for 
  a 
  short 
  distance 
  in 
  a 
  slightly 
  diverging 
  direction 
  

   toward 
  the 
  interior 
  of 
  the 
  shell. 
  There 
  is 
  no 
  median 
  septum 
  in 
  

   the 
  brachial 
  valve. 
  

  

  Type, 
  Terebratuloidea 
  Davidsoni, 
  Waagen. 
  

  

  Distribution. 
  Carboniferous 
  — 
  Permian. 
  

   129 
  83 
  

  

  