Yol.  49.] 
STRUCTURE  OF  THE  WENLOCK  LIMESTONE. 
247 
EXPLANATION  OF  PLATE  YI. 
Fig.  1.  Spherule  of  Girvanella ,  Wenlock  Limestone,  May  Hill,  X  16  diam. 
There  are  two  strata  of  tubules  surrounding  a  polvzoan  fragment.  The 
smaller  tubules  measure  '03  millim.  in  diameter,  and  do  not  surround 
the  whole  of  the  nucleus.  The  larger  tubules  measure  T4  millim. 
Fig.  2.  A  remarkably  fine  spherule  of  Girvanella  from  the  Wenlock  Limestone. 
.  May  Hill,  X  32  diam.  The  tubules  are  nearly  all  of  the  same  size, 
and  measure  about  TO  millim.  in  diameter. 
Fig.  3.  Spherule  of  Girvanella,  also  from  the  Wenlock  Limestone  of  May  Hill. 
X  32  diam.  In  this  there  are  two  strata  of  tubules  surrounding  a 
nucleus  of  calcite  ;  the  smaller  tubules  measure  -02  millim  in  diameter, 
and  the  larger  ’05  millim.  The  inner  stratum  of  tubules  is  not  con¬ 
tinuous  around  the  entire  nucleus,  but  passes  into  a  granulated  material, 
in  which,  however,  the  outlines  of  tubules  can  be  detected. 
Figs.  4  a  (X  32  diam.)  &  4  6  ( X  65  diam.).  Wenlock  Limestone,  May  Hill. 
Portion  of  a  64raz;?e£/ft-spkerule  remarkable  for  the  complicated 
structure  of  the  tubules.  Apparently  they  are  branching,  but  there 
are  some  markings  which  it  is  difficult  to  account  for.  The  tubules 
measure  '03  millim.  in  diameter. 
Fig.  5.  Girvanel/os-sipherule  from  the  Wenlock  Limestone,  Purley,  near  West 
Malvern.  The  spherule  is  remarkable  for  the  concentric  growth  of 
the  tubules.  These  measure  ’02  millim.  in  diameter.  X  65  diam. 
Fig.  6.  Represents  a  granule  from  the  Wenlock  Limestone  of  Purley,  near 
West  Malvern,  in  which  there  is  no  well-defined  tubular  structure. 
X  65  diam.  The  nucleus  is  an  ossicle  of  a  crinoid. 
Discussion. 
The  President  remarked  upon  the  very  great  interest  of  the 
paper.  It  appeared  that  the  Wenlock,  like  most  other  Palaeozoic 
limestones,  was  largely  composed  of  crinoids.  The  Author  seemed 
to  be  less  certain  with  regard  to  the  origin  of  Girvanella  than  he 
had  been  in  a  previous  communication,  which,  if  his  (the  speaker's) 
memory  served  him  aright,  contained  a  discussion  as-  to  the  kind 
of  foraminifer  to  which  Girvanella  should  he  referred.  Xow  the 
Author  regarded  it  as  probably  an  organism,  but  one  of  very  low 
type. 
Prof.  Bonnet  acknowledged  the  great  value  of  Mr.  Wethered’s 
admirable  researches.  It  was  very  interesting  to  notice  how 
the  action  of  living  organisms  was  being  detected  in  processes 
hitherto  deemed  simply  physical ;  as  in  the  formation  of  sinter  and 
tufa,  described  by  Mr.  W.  H.  Weed.  It  had  also  been  found  that 
calcareous  algae  were  important  constituents  in  the  formation  of 
certain  more  or  less  pisolitic  limestones  in  the  Eastern  Alps.  The 
insoluble  residues  from  these  Silurian  limestones,  which,  thanks  to 
Mr.  Wethered’s  kindness,  the  speaker  had  seen,  were  of  great 
interest :  some  largely  consisted  of  the  4  clotted  ’  siliceous  material, 
already  often  noticed  in  residues  :  others  of  fragmental  grains — 
quartz,  felspar,  zircon,  and  other  constituents  of  crystalline  rocks  in 
good  preservation.  He  thought  they  indicated  that  a  land  formed 
of  such  rocks  must  have  existed  at  no  very  great  distance. 
Dr.  G.  J.  Hinde  commended  the  way  in  which  the  Author  had 
brought  forward  his  paper  :  the  enlarged  photographs  exhibited  by 
him  very  distinctly  illustrated  the  character  and  variety  of  organic 
