﻿Report 
  of 
  the 
  State 
  Geologist. 
  949 
  

  

  2. 
  Aseptati. 
  Those 
  without 
  a 
  median 
  septum 
  in 
  the 
  pedicle- 
  

   valve. 
  These 
  species 
  are 
  more 
  abundantly 
  plicated, 
  often 
  much 
  

   more 
  extended 
  on 
  the 
  hinge 
  than 
  in 
  the 
  septate 
  group. 
  The 
  

   lamellae 
  are 
  without 
  radial 
  striations. 
  The 
  Aseptati 
  group 
  them- 
  

   selves 
  naturally 
  about 
  two 
  type-forms, 
  the 
  first, 
  (a) 
  Spirifer 
  

   mucronatus, 
  Conrad, 
  an 
  alate, 
  multiplicate 
  shell 
  with 
  a 
  single 
  low 
  

   plication 
  in 
  the 
  sinus 
  and 
  a 
  corresponding 
  depression 
  on 
  the 
  

   median 
  fold; 
  the 
  other, 
  (b) 
  Spirifer 
  submucronatus, 
  Hall, 
  in 
  which 
  

   the 
  fold 
  and 
  sinus 
  are 
  not 
  plicate. 
  

  

  Section 
  III. 
  Fimbbiati. 
  (Plate 
  25, 
  figs. 
  1-15.) 
  Typical 
  examples, 
  

   Spirifer 
  fimbriatus, 
  Conrad, 
  S. 
  lineatus, 
  Martin, 
  S. 
  arrectus, 
  Hall. 
  

  

  Shells 
  with 
  few 
  low 
  plications 
  or 
  none 
  ; 
  hinge 
  -line 
  not 
  greatly 
  

   extended, 
  often 
  shorter 
  than 
  the 
  greatest 
  diameter 
  of 
  the 
  shell 
  ; 
  

   dental 
  lamellae 
  moderately, 
  sometimes 
  notably 
  developed 
  ; 
  a 
  low 
  

   median 
  septum 
  may 
  exist 
  in 
  the 
  pedicle-valve. 
  Surface 
  covered 
  

   with 
  concentric 
  rows 
  of 
  fringes 
  or 
  fine 
  spines. 
  

  

  This 
  group 
  is 
  divided 
  into 
  : 
  

  

  1. 
  Unicispinei 
  = 
  Delthtris, 
  Dalman, 
  1828, 
  sensu 
  stricto; 
  

   those 
  species 
  in 
  which 
  the 
  concentric 
  fimbriae 
  are 
  made 
  up 
  of 
  

   short, 
  simple, 
  hollow 
  spines. 
  These 
  are 
  the 
  early 
  fimbriate 
  

   species, 
  the 
  type 
  of 
  structure 
  not 
  extending, 
  so 
  far 
  as 
  now 
  known, 
  

   beyond 
  the 
  Devonian. 
  The 
  shells 
  are 
  distinguished 
  from 
  the 
  

   other 
  fimbriate 
  Spirifers 
  by 
  their 
  more 
  extended 
  and 
  more 
  dis- 
  

   tinctly 
  plicated 
  surface 
  and 
  the 
  prominent, 
  often 
  sharply 
  devel- 
  

   oped 
  fold 
  and 
  sinus. 
  Their 
  more 
  characteristic 
  representatives 
  

   in 
  the 
  American 
  Palaeozoic 
  are 
  Spirifer 
  crisp 
  us, 
  Hisinger, 
  and 
  

   var. 
  simplex, 
  Hall, 
  of 
  the 
  Niagara 
  faunas; 
  S. 
  Vanuxemi, 
  Hall, 
  of 
  

   the 
  Tentaculite 
  limestone, 
  S 
  Sajfordi, 
  S. 
  octocostatus, 
  Hall, 
  of 
  the 
  

   Lower 
  Helderberg 
  group, 
  S. 
  arrectus, 
  S. 
  tribulis, 
  Hall, 
  of 
  the 
  

   Oriskany 
  sandstone 
  and 
  S. 
  duodenarius, 
  Hall, 
  of 
  the 
  Corniferous 
  

   limestone. 
  This 
  is 
  the 
  (a) 
  S. 
  crispustjipe. 
  

  

  An 
  interesting 
  series 
  of 
  forms 
  which 
  has 
  had 
  a 
  parallel 
  develop- 
  

   ment 
  with 
  the 
  S. 
  crispus-tyipe 
  begins 
  with 
  the 
  S. 
  bicostatus, 
  

   Yanuxem, 
  and 
  var. 
  petilus, 
  Hall, 
  in 
  the 
  Niagara 
  group, 
  is 
  repre, 
  

   sented 
  by 
  S. 
  modestus, 
  Hall, 
  in 
  the 
  Lower 
  Helderberg 
  group, 
  S. 
  

   Oanandaiguce, 
  from 
  the 
  Hamilton 
  group, 
  and 
  possibly, 
  S. 
  urbanus- 
  

   Calvin, 
  from 
  a 
  corresponding 
  horizon 
  in 
  Iowa, 
  the 
  line 
  terminat- 
  

   ing 
  in 
  (b) 
  S. 
  Icevis, 
  Hall, 
  from 
  the 
  lower 
  Portage 
  shales. 
  

  

  7 
  

  

  