﻿ON 
  THE 
  STRUCTURE 
  OF 
  ASTRJIOSPONGIA 
  MENISCUS. 
  

  

  By 
  Des. 
  J. 
  W. 
  HALL 
  and 
  R. 
  FRITZ-GAERTNER. 
  

  

  Professor 
  Ferdinand 
  Romer, 
  of 
  Breslau, 
  in 
  his 
  interesting 
  

   monograph 
  upon 
  the 
  Silurian 
  Fauna 
  of 
  Western 
  Tennessee,* 
  

   and 
  also 
  in 
  that 
  of 
  the 
  Silurian 
  Fossil 
  Fauna 
  of 
  Erratic 
  Boul- 
  

   ders 
  found 
  near 
  Sadewitz 
  in 
  Silesia, 
  f 
  has 
  given, 
  so 
  far 
  as 
  we 
  

   know, 
  the 
  fullest 
  description 
  of 
  this 
  peculiar 
  and 
  characteristic 
  

   fossil 
  of 
  the 
  Silurian 
  formation 
  of 
  Tennessee. 
  

  

  Referring 
  to 
  Professor 
  Romer, 
  we 
  find 
  this 
  fossil 
  character- 
  

   ized 
  as 
  round, 
  disc- 
  shaped, 
  concave 
  on 
  the 
  upper 
  and 
  convex 
  

   on 
  the 
  lower 
  side, 
  varying 
  in 
  shape 
  from 
  an 
  almost 
  flat 
  disc 
  to 
  

   the 
  form 
  of 
  a 
  cup. 
  

  

  The 
  surface 
  of 
  the 
  sponge 
  is 
  covered 
  with 
  regularly 
  shaped 
  

   stars 
  which 
  also 
  interlace 
  the 
  interior 
  of 
  the 
  sponge, 
  but 
  with- 
  

   out 
  regard 
  to 
  order. 
  , 
  The 
  branches 
  of 
  these 
  stars 
  are, 
  accord- 
  

   ing 
  to 
  this 
  author, 
  without 
  any 
  connection 
  with 
  those 
  adjacent. 
  

  

  Neither 
  could 
  Professor 
  Romer 
  find 
  any 
  pores 
  in 
  the 
  stars, 
  

   nor 
  any 
  indications 
  of 
  animal 
  tissue 
  in 
  the 
  interstices 
  in 
  or 
  

   among 
  them, 
  but 
  considered 
  them 
  only 
  as 
  spines 
  or 
  spiculse. 
  

   His 
  separation 
  of 
  the 
  genus 
  Astraeospongia 
  from 
  Astylospon- 
  

   gia 
  seems 
  to 
  be 
  chiefly 
  based 
  upon 
  the 
  want 
  of 
  regularity 
  in 
  the 
  

   structure 
  and 
  arrangement 
  of 
  the 
  component 
  parts 
  of 
  the 
  first, 
  

   and 
  the 
  uniform 
  relative 
  position 
  of 
  the 
  more 
  minute 
  stars 
  in 
  

   the 
  second, 
  namely, 
  their 
  various 
  branches 
  forming 
  direct 
  lines 
  

   one 
  with 
  the 
  other 
  throughout 
  the 
  sponge 
  ; 
  and 
  also 
  that 
  in 
  

   this 
  latter 
  genus, 
  there 
  exists 
  evidence 
  of 
  animal 
  matter. 
  

  

  A 
  large 
  collection 
  of 
  these 
  fossil 
  sponges, 
  from 
  the 
  same 
  

   localities 
  which 
  furnished 
  Professor 
  Romer 
  with 
  his 
  specimens, 
  

   having 
  been 
  kindly 
  placed 
  at 
  our 
  disposal, 
  for 
  study 
  and 
  com- 
  

   parison, 
  by 
  Professor 
  Hall, 
  Director 
  of 
  the 
  State 
  Museum, 
  

  

  * 
  Die 
  Silurische 
  Fauna 
  des 
  Westlichen 
  Tennessee. 
  1860. 
  

  

  f 
  Die 
  Fossile 
  Fauna 
  der 
  Silurischen 
  Diluvial-Gesckiebe 
  von 
  Sadewitz 
  bei 
  Oels, 
  in 
  

   Nieder 
  Schlesien. 
  1861. 
  

  

  