﻿986 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  plications, 
  much 
  finer 
  than 
  those 
  adjoining 
  on 
  each 
  side. 
  Shell 
  

   substance 
  rather 
  sparsely 
  punctate. 
  

  

  Type, 
  Rhynchospira 
  formosa, 
  Hall. 
  Lower 
  Helderberg 
  group. 
  

  

  Distribution. 
  Devonian 
  — 
  Lower 
  Carboniferous. 
  

  

  Subgenus 
  Homoeospira, 
  Hall. 
  1893. 
  

   (Plate 
  36, 
  figs. 
  13-19.) 
  

  

  Shells 
  similar 
  in 
  exterior 
  to 
  Rhynchospira. 
  The 
  hinge-plate 
  

   has 
  no 
  posterior 
  extension, 
  but 
  its 
  anterior 
  lobes 
  are 
  greatly 
  

   developed 
  into 
  long, 
  divergent 
  crural 
  bases. 
  They 
  are 
  separated 
  

   to 
  the 
  apex 
  of 
  the 
  beak 
  and 
  between 
  them 
  lies 
  a 
  small 
  linear 
  car- 
  

   dinal 
  process. 
  There 
  is 
  a 
  stout 
  median 
  septum 
  in 
  the 
  brachial 
  

   valve 
  whose 
  height 
  is 
  equal 
  to 
  nearly 
  one-half 
  the 
  depth 
  of 
  the 
  

   valve. 
  The 
  jugum 
  has 
  an 
  acute 
  stem 
  and 
  its 
  lateral 
  branches 
  are 
  

   of 
  the 
  same 
  width 
  from 
  their 
  origin 
  to 
  the 
  point 
  of 
  union. 
  The 
  

   deltidial 
  plates 
  frequently 
  remain 
  distinct 
  and 
  uncoalesced 
  at 
  

   maturity. 
  

  

  (Type, 
  Homoeospira 
  evax, 
  Hall. 
  Magara 
  group.) 
  

  

  Ptychospira, 
  Hall. 
  1893. 
  

   (Plate 
  36, 
  figs. 
  20-23.) 
  

   Shells 
  bearing 
  a 
  few 
  sharply 
  angular 
  radial 
  plications 
  which 
  

   are 
  greatly 
  elevated 
  at 
  the 
  margins 
  of 
  the 
  shell. 
  The 
  median 
  

   plication 
  on 
  the 
  brachial 
  valve 
  is 
  usually 
  divided 
  by 
  a 
  fine 
  sulcus, 
  

   there 
  being 
  a 
  corresponding 
  ridge 
  in 
  the 
  sinus 
  of 
  the 
  opposite 
  

   valve. 
  The 
  beak 
  of 
  the 
  pedicle- 
  valve 
  is 
  erect, 
  and 
  truncated 
  

   obliquely 
  by 
  a 
  circular 
  foramen, 
  beneath 
  which 
  lies 
  a 
  flat 
  delta- 
  

   rium, 
  the 
  plates 
  of 
  which 
  are, 
  as 
  in 
  allied 
  genera, 
  more 
  or 
  less 
  

   completely 
  coalesced. 
  The 
  ep. 
  dermal 
  layer 
  of 
  the 
  shell 
  is 
  finely 
  

   pitted, 
  the 
  punctations 
  apparently 
  not 
  continuing 
  into 
  the 
  layers 
  

   beneath, 
  but 
  producing 
  a 
  superficial 
  ornamentation 
  not 
  unlike 
  

   that 
  occurring 
  in 
  Eichwaldia. 
  This 
  ornamented 
  layer 
  extends 
  

  

  even 
  over 
  the 
  surface 
  of 
  the 
  deltidium 
  . 
  

   The 
  inner 
  laminas 
  of 
  the 
  shell 
  are 
  fibrous 
  

   and 
  more 
  sparsely 
  punctated. 
  There 
  

   is 
  no 
  deltidial 
  tube 
  in 
  the 
  umbonal 
  cav- 
  

   ity 
  of 
  the 
  pedicle-valve. 
  The 
  hinge- 
  

   fig. 
  36o.-The 
  jugum 
  of 
  ptycho. 
  plate 
  appears 
  to 
  be 
  similar 
  to 
  that 
  

  

  spiraferita, 
  von 
  BuchisvO. 
  Q 
  f 
  R 
  H 
  YNCHOSPIRA, 
  with 
  UO 
  prominent 
  

  

  posterior 
  extension, 
  but 
  with 
  conspicuous 
  crural 
  bases 
  which 
  

   are 
  curved 
  upward. 
  The 
  whole 
  process 
  is 
  supported 
  by 
  

  

  44 
  

  

  