﻿Report 
  oi 
  the 
  State 
  Geologist. 
  

  

  1073 
  

  

  Subgenus 
  Rhaetina, 
  Waagen. 
  1882. 
  

  

  Shells 
  biplicate 
  ; 
  loop 
  short, 
  supported 
  by 
  crural 
  plates 
  ; 
  dental 
  

   plates 
  absent. 
  

  

  Figs. 
  548-551. 
  Rhaetina 
  gregaria, 
  guess 
  (sp.). 
  (Zugmayer.) 
  

  

  (Type, 
  Rhaetina 
  gregaria, 
  Suess 
  (sp.). 
  Triassic.) 
  

  

  Subgenus 
  Dictyothyris, 
  Douville. 
  1880. 
  

  

  Shells 
  subnaviculate, 
  with 
  median 
  fold 
  and 
  sinus 
  on 
  brachial 
  

   and 
  ^ 
  pedicle- 
  valves 
  respectively. 
  Surface 
  covered 
  with 
  short 
  

   spinules. 
  Dental 
  plates 
  are 
  present 
  in 
  the 
  pedicle-valve. 
  In 
  the 
  

  

  Figs. 
  552-555. 
  Dictyothyris 
  coarctata, 
  Parkinson 
  (sp.). 
  (Davidson.) 
  

  

  brachial 
  valve 
  is 
  a 
  well-developed 
  cardinal 
  process 
  and 
  faint 
  

   median 
  septum 
  ; 
  the 
  loop 
  is 
  short, 
  its 
  anterior 
  band 
  being 
  broad 
  

   and 
  considerably 
  reflected. 
  

  

  (Type, 
  Dictyothyris 
  coarctata, 
  Parkinson 
  (sp.). 
  Jurassic.) 
  

  

  Magellania, 
  Bayle. 
  1880. 
  

   Synonym; 
  Waldheimia, 
  King. 
  1850 
  ; 
  Neothyris, 
  Douville. 
  1880. 
  

   Shells 
  biconvex, 
  ovate 
  or 
  subpentagonal. 
  Surface 
  plicate 
  or 
  

   smooth. 
  Beak 
  of 
  the 
  pedicle- 
  valve 
  broadly 
  truncated. 
  Deltidial 
  

   135 
  131 
  

  

  