﻿104 
  TwEXTY-EIGUTH 
  KePORT 
  OK" 
  THE 
  STATE 
  MUSEUM. 
  

  

  This 
  widely 
  distributed 
  species 
  which 
  has 
  been 
  illustrated 
  

   by 
  Goldfuss, 
  Hisinger, 
  Bronn, 
  Eoemer 
  and 
  other 
  authors, 
  is 
  a 
  

   common 
  form 
  at 
  Waldron, 
  but 
  it 
  rarely 
  or 
  never 
  attains 
  the 
  

   dimensions 
  which 
  it 
  has 
  in 
  the 
  same 
  horizon 
  in 
  Tennessee, 
  

   where 
  it 
  is 
  even 
  more 
  common 
  than 
  in 
  Indiana. 
  

  

  The 
  usual 
  dimensions 
  of 
  the 
  Waldron 
  specimens 
  vary 
  from 
  

   ten 
  to 
  twenty 
  millimetres 
  in 
  lateral 
  diameter, 
  with 
  a 
  vertical 
  

   diameter 
  of 
  about 
  one- 
  sixth 
  less 
  than 
  the 
  lateral. 
  There 
  is 
  

   much 
  variation 
  in 
  the 
  strength 
  and 
  number 
  of 
  the 
  furrows 
  

   and 
  prominence 
  of 
  the 
  lobes, 
  and 
  also 
  in 
  the 
  depth 
  and 
  diam- 
  

   eter 
  of 
  the 
  depression 
  at 
  the 
  center 
  of 
  the 
  summit. 
  

  

  The 
  interior 
  structure 
  is 
  represented 
  in 
  figs. 
  9, 
  10, 
  11, 
  as 
  it 
  

   appears 
  under 
  an 
  ordinary 
  lens. 
  In 
  all 
  the 
  specimens 
  which 
  

   have 
  been 
  cut, 
  there 
  is 
  evidence 
  of 
  an 
  original 
  central 
  cavity, 
  

   filled 
  with 
  mineral 
  matter 
  which 
  does 
  not 
  preserve 
  structure. 
  

  

  ASTYLOSPONGIA 
  PR^EilORSA 
  Var. 
  NUXMOSCHATA 
  71. 
  VCLT. 
  

  

  Plate 
  3, 
  Figs. 
  12, 
  13. 
  

  

  Form, 
  an 
  oblate 
  spheroid 
  with 
  the 
  entire 
  surface 
  traversed 
  

   by 
  numerous 
  interrupted 
  and 
  unequal 
  grooves 
  or 
  subconflu- 
  

   ent 
  pits 
  giving 
  a 
  rugose 
  aspect 
  ; 
  the 
  sides 
  marked 
  by 
  a 
  few 
  nar- 
  

   row 
  scarcely 
  defined 
  sulci 
  which 
  do 
  not 
  reach 
  the 
  summit 
  ; 
  

   summit 
  elevated 
  and 
  without 
  the 
  central 
  depression 
  possessed 
  

   by 
  typical 
  forms 
  of 
  the 
  species. 
  Entire 
  surface 
  covered 
  by 
  

   minute 
  pustulose 
  elevations 
  which 
  under 
  an 
  ordinary 
  lens 
  do 
  

   not 
  show 
  structure. 
  The 
  minute 
  interior 
  structure 
  has 
  not 
  

   been 
  determined. 
  

  

  This 
  form 
  was 
  included 
  under 
  A.prcemorsa 
  in 
  the 
  Documen- 
  

   tary 
  edition 
  of 
  this 
  report. 
  It 
  is 
  herewith 
  separated 
  as 
  a 
  vari- 
  

   ety. 
  It 
  occurs 
  in 
  association 
  with 
  the 
  other 
  forms 
  of 
  Petro- 
  

   spongia 
  at 
  the 
  Waldron 
  locality. 
  

  

  ASTYLOSPONGIA 
  IXBEICATO-AETICULATA 
  F. 
  Roem. 
  

  

  Siphonia 
  imbricato-articulata 
  Ferd. 
  Roemer, 
  in 
  Leonh. 
  uud 
  Broim's 
  Jahrb. 
  1848, 
  

  

  685, 
  ix, 
  fig. 
  3. 
  

   Astylospongia 
  imbricato-articulata 
  F. 
  Roem. 
  Die 
  'Siiur. 
  Fauu. 
  desWestl. 
  Tenii., 
  

  

  p. 
  12, 
  pi. 
  1, 
  figs. 
  5, 
  5 
  a. 
  1860. 
  

  

  A 
  single 
  specimen 
  of 
  this 
  species 
  or 
  a 
  closely 
  allied 
  form, 
  

   has 
  been 
  observed 
  among 
  some 
  recent 
  collections 
  from 
  Wald- 
  

   ron. 
  

  

  