218  DISCUSSION - COAST-SECTIONS  AT  THE  LIZARD,  AND  [May  1 893, 
EXPLANATION  OF  PLATE  IV. 
Fig.  1.  Cenosphcsra,  sp.  Drawn  from  a  specimen  weathered  out  on  the  surface 
of  a  slab  of  chert.  X  200  diameters. 
Fig.  2.  Carposphoera,  sp.  a.  Drawn  from  a  microscopic  section.  X  200. 
Fig.  3.  Carposphcera,  sp.  b.  X  200. 
Fig.  4.  Cenellipsis,  sp.  a.  Showing  the  wall  in  section.  X  200. 
Figs.  5,  6.  Cenellipsis,  sp.  b.  One  specimen  showing  the  wall  in  section,  and 
the  other  showing  traces  of  the  lattice-work.  A  quartz-vein  traverses 
a  portion  of  this  latter.  X  200. 
Fig.  7.  Cenellipsis ,  sp.  c.  A  specimen  showing  the  lattice- structure  preserved 
in  dark  material.  X  200. 
Fig.  8.  Litkapium,  sp.  Showing  indistinct  traces  of  the  lattice-structure. 
X  200. 
Fig.  9.  Lithatradus,  sp.  Showing  the  form  in  section.  X  200. 
Fig.  10.  Outline  of  undetermined  form  with  three  radial  spines.  X  100. 
Fig.  11.  Specimen  undetermined,  the  outline  only  shown.  X  100. 
Fig.  12.  A  portion  of  a  slab  of  chert,  showing  radiolaria  partially  weathered 
out  on  its  surface.  X  50. 
Fig.  13.  Section  illustrating  the  structure  of  the  greenstone  associated  with 
the  chert  of  Mullion  Island.  Two  porphyritic  crystals  of  felspar  and 
acicular  microlites  of  the  same  mineral  are  clearly  recognizable  in  the 
figure,  x  50. 
All  the  specimens  are  from  the  chert  at  Mullion  Island,  Cornwall. 
Discussion  (on  the  two  preceding  papers). 
The  President  commented  on  the  many  difficulties  felt  by 
De  la  Beche  which  were  still  unsolved.  It  was  difficult  to 
know  whether  the  serpentine  was  intrusive  in  the  hornblende- 
schists,  or  vice  versa.  At  the  previous  Meeting  a  similar  question 
was  being  discussed  with  regard  to  the  Hebrides,  viz.  whether 
there  the  acid  rock  was  intrusive  in  the  basic  or  vice  versa.  If  he 
might  venture  on  a  surmise,  might  not  the  Lizard  rocks  form  an 
igneous  complex,  where  each  observer  paid  particular  attention  to 
those  points  bearing  on  his  own  views  ?  The  position  had  been 
advanced  a  point  further  by  the  Authors.  He  suggested  that  the 
discovery  of  organisms  in  Mullion  Island  might  throw  light  on 
the  period  to  which  the  complex  belonged,  though  it  was  not  clear 
that  the  Mullion  Island  rocks  were  of  the  same  age  as  those  of  the 
mainland.  It  seemed  that  Dr.  Hinde  could  not  determine  the  age 
of  the  radiolaria. 
Bev.  Edwin  Hill  spoke  of  the  interest  of  this  paper  on  Mullion 
Island.  The  Lizard  serpentine  seemed  ringed  in  by  other  rocks  ; 
in  this  respect  it  resembled  an  igneous  4  plug/  and  such  was  the 
impression  left  on  him  by  the  general  view  of  the  aggregate  of 
evidence.  While  these  papers  on  a  small  area  were  most  valuable, 
he  hoped  that  the  Authors  would  some  day  furnish  a  view  of  the 
Lizard  as  a  whole.  A  harmony  of  diverse  views  had  been  sug¬ 
gested  ;  he  doubted  if  it  were  desirable  to  attempt  this. 
Prof.  Bonnet  said  that  the  discovery  of  radiolarian  chert  at 
Mullion  Island  (which  he  had  not  visited)  was  of  great  interest,  but 
it  would  never  help,  as  the  President  seemed  to  think,  in  deter¬ 
mining  the  age  of  the  Lizard  schists.  He  believed  there  was  a 
