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DR.  G.  J.  HINDE  ON  THE  RADIOLARIA  [May  1 893, 
more  than  an  approximate  determination  of  the  genera  to  which  the 
radiolaria  belong,  and  in  some  cases  even  the  generic  position  is 
doubtful.  The  genera  recognizable  are  Cenosphcera ,  Ehrenberg, 
Carposphcera,  Haeckel,  Oenellipsis ,  Haeckel,  Lithapium ,  Haeckel,  and 
Lithatractus,  Haeckel,  belonging  to  the  two  sub-orders  of  the 
Sphseroidea  and  Prunoidea.  The  commonest  forms  present  are 
simple,  spherical  or  oval  lattice-tests  belonging  to  Cenosphcera 
(PI.  IV.  fig.  1)  and  Oenellipsis  (PI.  IY.  figs.  4-7).  The  tests  range 
from  *16  to  -30  mm.  in  diameter.  The  genus  Carposphoera ,  in  which 
there  are  two  concentric  lattice-tests,  is  represented  by  a  few 
small  forms  (PI.  IY.  figs.  2  and  3)  which  may  perhaps  belong  to 
two  species.  A  specimen  with  an  elliptical  lattice -test  and  a  single 
spine  (PI.  IY.  fig.  8)  is  included  under  Lithapium ,  and  other 
examples  with  two  concentric  tests  and  with  a  spine  at  each  pole 
(PI.  IY.  fig.  9)  belong  to  Lithatractus.  Eorms  with  spines  are 
comparatively  rarely  shown  in  sections  ;  in  the  two  examples  figured 
(PI.  IY.  figs.  10  and  11)  only  the  outlines  are  seen,  and  they  do  not 
appear  to  belong  to  any  genus  yet  described.  The  recognizable 
forms  belong  to  simple  generic  types  which  are  all  represented 
in  Palaeozoic  strata,  and  with  one  exception  as  low  as  the  Silurian, 
but  they  do  not  afford  any  trustworthy  indication  of  the  age  of  the 
chert  in  which  they  occur. 
With  the  exception  of  the  radiolaria,  the  only  other  microscopic 
organic  remains  in  sections  of  the  chert  are  some  ill-defined  spicular 
bodies,  shown  only  in  the  dark-stained  portion  of  the  rock ;  some  of 
these  may  be  fragmentary  spines  of  radiolaria,  while  others  are 
perhaps  spicules  of  siliceous  sponges. 
The  following  is  a  technical  description  of  the  forms  which  can 
be  recognized : — 
Sub-order  Sph^roidea,  Haeckel. 
Cenosphcera ,  sp.,  PI.  IY.  fig.  1. 
Spherical  tests,  ranging  from  *145  to  *305  mm.  in  diameter,  are 
numerous  in  the  chert,  but  the  lattice-structure  is  shown  only  in 
those  weathered  out  on  the  surface.  The  holes  in  the  test  appear 
to  be  subequal,  about  *015  mm.  in  breadth,  while  the  lattice-work 
is  from  *005  to  *010  mm.  wide.  In  the  size  and  disposition  of  the 
apertures  of  the  test,  this  form  resembles  O.  gregaria ,  Rust  (‘  Palaeon- 
tographica,’  vol.  xxxi.  1885,  p.  286,  pi.  xxvi.  fig.  10),  which  is 
common  alike  in  Devonian,  Jurassic,  and  Cretaceous  strata. 
Carposphoera ,  sp.  a ,  PI.  IY.  fig.  2. 
The  outer  test  is  *145  mm.  in  diameter  and  *009  mm.  in  thick¬ 
ness,  and  the  inner  *045  mm.  in  breadth.  The  structure  is  not 
preserved.  There  are  three  rays  visible,  connecting  the  inner  with 
the  outer  test.  It  resembles  in  outline  C.  pygmcea ,  Riist,  from  the 
Lower  Carboniferous  of  the  Harz  (‘  Palseontographica,’  vol.  xxxviii. 
1892,  p.  135,  pi.  vi.  fig.  13),  but  it  is  distinctly  larger.  The  form 
is  rare. 
