114  PROCEEDINGS  Or  THE  GEOLOGICAL  SOCIETY.  [May  1893, 
as  the  representative  of  the  4  Sponge-bed  ’  of  Hunstanton.  This 
can  also  he  traced  in  Yorkshire  as  far  as  the  north-western  ex¬ 
tremity  of  the  Wolds.  Above  this  bed  a  few  feet  of  grey  gritty 
chalk  retain  the  character  of  the  Hunstanton  4  Inocercimus- bed  ’ 
throughout  the  area  above  mentioned.  In  the  same  district  also  a 
well-known  rock  called  the  4  Grey  Bed'  is  shown  to  be  on  the  horizon 
of  the  Totternhoe  Stone,  and  thus  to  determine  the  upper  limit  of 
the  Chalk  Marl ;  this  bed  is  characterized  by  much  comminuted 
shelly  matter  and  by  numerous  Pectens  amongst  other  fossils.  The 
Author  notes,  moreover,  the  red  coloration  of  portions  of  the  Grey 
Chalk  in  Lincolnshire,  the  principal  horizons  for  this  coloration 
being  just  above  the  Grey  Bed  and  a  little  below  the  Lincolnshire 
equivalent  of  the  Melbourn  Bock. 
When  the  basement-beds  of  the  Upper  Cretaceous  are  traced  from 
their  most  attenuated  outcrop,  600  feet  above  sea-level,  at  the  north¬ 
western  extremity  of  the  Wolds,  towards  the  sea,  there  is  every  reason 
to  believe  that  they  rapidly  thicken  again,  and  when  the  coast  at 
Speeton  is  attained  the  whole  series  is  found  to  be  expanded  to  a 
thickness  nearly  four  times  greater  than  at  Leavening  on  the  Wolds, 
and  more  than  twice  as  great  as  at  Hunstanton.  The  thickening  is 
shared  by  all  the  series  below  the  zone  of  Rhynchonella  Cuvieri  (at 
the  base  of  the  Middle  Chalk),  where  flints,  as  a  rule,  first  make  their 
appearance.  This  classical  section  is  described  with  much  care  by 
Mr.  Hill,  and  many  new  points  of  interest  are  brought  out,  though 
time  will  not  allow  me  to  do  justice  to  them.  I  will  only  quote  one 
passage  for  the  benefit  of  those  who  place  their  faith  in  flints  as  a 
means  of  determining  horizons  in  the  Chalk.  He  says : — 44  The  gradual 
approach  of  the  Chalk- with -flints  to  the  Lower  Chalk  should  be  noted, 
and  the  value  of  flints  for  stratigraphical  purposes  may  be  estimated 
from  the  following  facts  : — at  Hover  they  are  120  feet  above  the  zone 
of  Belemnitella  plena ;  at  Hitchin  the  first  line  of  flints,  followed 
by  others  at  distant  intervals,  occurs  about  45  feet  above  the  base 
of  the  Middle  Chalk.  In  Lincolnshire  flints  occur  in  regular  lines 
.  .  .  .  only  15  feet  above  the  Belemnite-marls,  and  this  is  reduced 
by  nearly  one  half  at  Speeton,  where  flints  come  on  8  feet  above 
the  Marls/’  Moreover,  at  Speeton,  beds  of  flints,  some  yards  in 
extent,  occur  in  the  higher  portion  of  the  Chalk  Marl  itself. 
Mr.  Hill,  as  is  well  known,  has  paid  much  attention  to  the  minute 
structure  of  the  various  chalks.  With  reference  to  the  composition 
of  the  Bed  Chalk  or  Hunstanton  Limestone  in  Lincolnshire  and 
along  the  western  escarpment  of  the  Yorkshire  Wolds,  he  observes 
