Il8  PROCEEDINGS  OE  THE  GEOLOGICAL  SOCIETY.  [May  1 893, 
sediments  give  way  to  those  of  a  calcareous  nature.  Hence  this 
had  been  an  area  of  marine  deposition  throughout  a  long  period 
of  Mesozoic  time,  although  at  no  great  distance  to  the  westward 
there  must  have  been  an  axis  of  upheaval  in  the  interval  of  time 
between  the  Eimeridge  Clay  and  the  Red  Chalk.  In  point  of  fact, 
he  considers  that  part  of  the  material  removed  from  this  area  of 
denudation  to  the  westward  may  possibly  have  contributed  to  the 
formation  of  the  Speeton  Clays  themselves.  However  this  may  be- 
he  justly  regards  the  series  of  beds  collectively  known  as  the 
4  Speeton  Clay/  though  probably  not  more  than  300  feet  thick, 
as  by  far  the  most  important  exposure  of  marine  beds  of  Lower 
Cretaceous  age  in  England,  and  possibly  in  Europe. 
Accepting  Mr.  Lamplugh  as  our  guide,  we  may  venture  to  consider 
the  Speeton  section  somewhat  in  detail,  proceeding  from  higher  to 
lower  horizons.  The  zone  of  Belemnites  minimus  and  its  allies  has 
already  been  referred  to  in  dealing  with  the  Upper  Cretaceous. 
The  second  zone  is  somewhat  obscured  towards  its  upper  part,  and 
it  is  ouly  the  lower  part  of  the  zone  which  the  Author  ventures  to 
describe  with  any  degree  of  certainty.  Belemnites  brunsvicensis, 
Stromb.  ( semicanaliculcitus  ?),  is  the  distinguishing  Eelemnite. 
Ammonites  are  said  to  be  rare  in  this  portion  of  the  section,  the 
most  characteristic  being  Hoplites  Deshciyesii .  The  fauna  generally 
tends  to  prove  that  this  portion  of  the  section  corresponds  with  the 
Lower  Greensand  and  Atherfield  Clay  of  the  South  of  England, 
which  may  be  regarded  as  of  Aptian  age.  In  Lincolnshire  the 
Tealby  Limestone  is  stated  to  represent  this  zone,  which  has  also 
been  recognized  in  Central  Russia.  It  is  quite  possible  that  the 
correlation  of  this  zone  at  Speeton  with  beds  in  the  South  of  England 
can  only  be  approximate,  since  it  scarcely  seems  fair  to  associate 
Hoplites  Deshayesii  with  the  whole  of  a  zone,  in  so  large  a  portion 
of  which  that  Ammonite  has  not  yet  been  discovered. 
The  third,  zone  may  be  regarded  as  the  backbone  of  the  Speeton 
section,  and  it  is  on  the  whole  perhaps  the  most  interesting  and 
apparently  the  most  fossiliferous,  since  the  more  typical  Speeton 
forms,  such  as  Ammonites  speetonensis ,  Am.  regalis  (noricus),  Crioceras 
?  JDuvalii,  Meyeria  ornata ,  etc.,  occur  more  or  less  abundantly 
throughout  certain  horizons  of  this  zone.  Moreover,  the  measure¬ 
ments  are  complete,  showing  a  thickness  of  about  120  feet.  Belem¬ 
nites  which  may  be  grouped  under  the  collective  title  of  Bel. 
jaculum,  in  which  Prof.  Pavlow  recognizes  at  least  3  species,  pre¬ 
dominate  throughout  this  series  of  clays.  Among  the  Ammonites 
