﻿Report 
  of 
  the 
  State 
  Geologist. 
  981 
  

  

  Euractinella, 
  Bittner. 
  1890. 
  

   Shells 
  with 
  short 
  corresponding 
  ribs, 
  obscure 
  cardinal 
  area 
  

   and 
  double 
  spirals. 
  

  

  Figs. 
  334, 
  335. 
  Euractinella 
  contraplecta, 
  Miinster 
  (sp.). 
  (Bittxer.) 
  

  

  Type, 
  Euractinella 
  contraplecta, 
  Miinster 
  (sp.). 
  

   Distribution. 
  Triassic. 
  

  

  Anisactinella, 
  Bittner. 
  1890. 
  

   Shells 
  with 
  the 
  ribs 
  on 
  the 
  valves 
  alternating 
  in 
  position 
  ; 
  car- 
  

   dinal 
  area, 
  deltarium 
  and 
  cardinal 
  process 
  well 
  developed. 
  

   Spiral 
  cones 
  duplex, 
  the 
  intercalary 
  cones 
  giving 
  off 
  a 
  process 
  in 
  

  

  Figs. 
  336-338. 
  Anisactinella 
  quadriplecta^Munster 
  (sp.). 
  (Bittner.) 
  

  

  umbonal 
  region 
  which 
  returns 
  to 
  join 
  the 
  jugum, 
  as 
  in 
  Merista 
  

   and 
  Meristella. 
  

  

  Type, 
  Anisactinella 
  quadrijrtecta, 
  Miinster 
  (sp.). 
  

  

  Distribution. 
  Triassic. 
  

  

  Retzia, 
  King. 
  1850. 
  

   (Plate 
  36, 
  figs. 
  3-7.) 
  

   Shell 
  elon 
  gate-oval, 
  rather 
  broad 
  over 
  the 
  pallial 
  region. 
  

   Surface 
  covered 
  with 
  rather 
  coarse, 
  angular, 
  usually 
  simple 
  

   plications. 
  There 
  is 
  a 
  trace 
  of 
  an 
  indistinct 
  median 
  sinus 
  on 
  the 
  

   pedicle-valve 
  in 
  which 
  the 
  plications 
  are 
  slightly 
  smaller 
  than 
  

   those 
  adjoining. 
  The 
  umbo 
  of 
  the 
  pedicle-valve 
  is 
  incurved 
  and 
  

   its 
  apex 
  truncated 
  by 
  a 
  circular 
  foramen. 
  The 
  deltidial 
  covering 
  

   is 
  triangular, 
  flat 
  or 
  arched 
  by 
  the 
  incurvature 
  of 
  the 
  beak 
  ; 
  the 
  

   deltidial 
  plates 
  are 
  firmly 
  anchylosed 
  into 
  a 
  single 
  piece 
  and 
  the 
  

   original 
  line 
  of 
  symphysis 
  is 
  represented 
  by 
  a 
  thickened 
  ridge. 
  

   The 
  edges 
  of 
  the 
  cardinal 
  area 
  are 
  well 
  defined, 
  but 
  not 
  alate 
  on 
  

   either 
  valve, 
  the 
  beak 
  and 
  area 
  of 
  the 
  brachial 
  valve 
  being 
  

  

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