﻿950 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum, 
  

  

  2. 
  Duplicispinei 
  == 
  Reticularia, 
  McCoy, 
  1844; 
  those 
  species 
  

   in 
  which 
  the 
  fimbriae 
  are 
  composed 
  of 
  large, 
  compound, 
  hollow 
  

   spines, 
  often 
  or 
  always 
  with 
  lateral 
  branches. 
  Each 
  spine 
  is 
  

   divided 
  medially 
  b} 
  T 
  a 
  vertical 
  septum, 
  and 
  along 
  this 
  line 
  the 
  

   spine 
  is 
  depressed 
  exteriorly, 
  giving 
  it 
  a 
  double 
  barreled 
  appear- 
  

   ance 
  ; 
  from 
  each 
  lateral 
  margin 
  are 
  given 
  off 
  at 
  regular 
  intervals 
  

   short 
  spinules 
  at 
  right 
  angles 
  to 
  the 
  main 
  spine. 
  (8. 
  Jlmbriatus, 
  

   Conrad; 
  8. 
  subundiferus, 
  Meek 
  and 
  Worthen 
  ; 
  8. 
  hirtus, 
  White 
  

   and 
  Whitfield 
  ; 
  8. 
  lineatus, 
  Martin.) 
  

  

  Section 
  IV. 
  Aperturati. 
  (Plate 
  26, 
  figs. 
  1-10.) 
  Typical 
  ex- 
  

   amples, 
  8. 
  aperturatus, 
  Schlotheim, 
  8. 
  disjunctus, 
  Sowerby 
  

   8. 
  siriatus, 
  Martin. 
  

  

  Forms 
  with 
  plications 
  on 
  the 
  fold 
  and 
  sinus. 
  

  

  This 
  may 
  be 
  regarded 
  as 
  the 
  typical 
  group 
  of 
  Spirifers 
  as 
  it 
  

   includes 
  the 
  type-species, 
  8. 
  striatus, 
  Martin. 
  Furthermore 
  it 
  is 
  

   the 
  most 
  richly 
  represented 
  in 
  species 
  and 
  at 
  the 
  same 
  time 
  is 
  a 
  

   most 
  compact 
  association, 
  not 
  presenting 
  any 
  substantial 
  varia- 
  

   tions. 
  Its 
  members 
  are 
  strongly 
  impressed 
  with 
  the 
  typical 
  spir- 
  

   iferoid 
  characters 
  which 
  are 
  maintained 
  throughout 
  its 
  existence, 
  

   the 
  group 
  terminating 
  abruptly 
  at 
  the 
  close 
  of 
  palaeozoic 
  time. 
  

   In 
  internal 
  structure 
  variations 
  are 
  slight 
  and 
  unimportant. 
  The 
  

   dental 
  lamellae 
  are, 
  as 
  a 
  rule, 
  inconsiderably 
  developed, 
  and 
  there 
  

   is 
  no 
  median 
  septum 
  in 
  either 
  valve. 
  

  

  (a) 
  Disjunctus-type. 
  Forms 
  with 
  well 
  developed 
  fold 
  and 
  sinus, 
  

   elongate 
  hinge 
  and 
  elevated 
  cardinal 
  area 
  ; 
  lateral 
  plications 
  

   simple, 
  median 
  plications 
  dichotomous 
  or 
  intercalary. 
  

  

  (Spirifer 
  arenosus, 
  Conrad, 
  Oriskany 
  sandstone 
  ; 
  Spirifer 
  uni- 
  

   ons. 
  Hall, 
  Corniferous 
  limestone 
  ; 
  Spirifer 
  Whitney 
  'i, 
  Hall, 
  Lower 
  

   upper 
  Devonian 
  ; 
  Spirifer 
  disjunctus, 
  Sowerby, 
  Chemung 
  group.) 
  

  

  A 
  subordinate 
  division 
  of 
  this 
  section 
  is 
  the 
  

  

  (1) 
  Hungerfordi-type 
  (=Choristites, 
  Fischer 
  de 
  Waldheim, 
  

   1>25), 
  in 
  which 
  the 
  fold 
  and 
  sinus 
  are 
  low, 
  often 
  obsolescent, 
  the 
  

   outline 
  suborbicular 
  and 
  the 
  cardinal 
  area 
  compressed 
  laterally 
  

   and 
  incurved 
  ; 
  dental 
  lamellae 
  prominently 
  developed. 
  This 
  type 
  

   is 
  represented 
  by 
  8. 
  Hungerfordi, 
  Hall, 
  of 
  the 
  lower 
  Upper 
  

   Devonian. 
  

  

  (b) 
  Striatus-type. 
  Forms 
  having 
  a 
  great 
  number 
  of 
  duplicate 
  

   lateral 
  plications, 
  well 
  developed, 
  rarely 
  acuminate 
  fold 
  and 
  sinus, 
  

   and 
  narrow, 
  usually 
  extended 
  cardinal 
  area. 
  

  

  8 
  

  

  