Yol.  49.]  AXXIVEESABY  ADDEESS  OE  THE  PEESIBEXT.  121 
period  of  time  may  be  represented  by  these  four  inches  of  phosphatic 
nodules.  The  list  of  recognizable  fossils  is  a  very  small  one  ;  but 
there  are  those  phantom  forms,  so  characteristic  of  nodule-beds, 
which  most  probably  represent  the  defaced  casts  and  other  hard 
parts  of  an  elutriated  formation.  This,  then,  was  an  area  of  sub¬ 
marine  erosion,  which  apparently  lasted  so  long  that  when  depo¬ 
sition  again  set  in  the  fauna  was  no  longer  the  same.  There  seems 
to  have  been  something  of  the  sort,  though  less  marked,  in  connexion 
with  the  4  Compound  X odular  Band,’  which  separates  the  laterdlis- 
zone  from  the  zone  of  Bel.  jaculum.  Here,  as  we  have  seen,  a  great 
mixture  of  forms  occurs  :  but  the  presence  of  Gnoceras ,  for  the  first 
time  in  the  Speeton  section,  seems  to  show  that  this  bed  should 
be  regarded  as  the  base  of  the  series  of  clays  which  succeed,  and 
which  the  Author  regards  as  marking  the  commencement  of  the 
Neocomian  in  this  part  of  Yorkshire. 
Jueassic  Geology,  lncltldixg  Rhaetic. 
Upper  Jurassic. — In  Lincolnshire  the  late  Hr.  Roberts  endeavoured 
to  make  a  triple  division  of  the  Upper  Jurassic  Clays.  He  called 
to  mind  that  Prof.  Seeley  had  previously  divided  the  Pen  clays  of 
Cambridgeshire  into  Kimeridge  Clay,  Ampthill  Clay  (regarded  as  of 
Corallian  age),  and  Oxford  Clay.  The  task  Hr.  Roberts  imposed 
upon  himself  was  certainly  a  very  difficult  one,  seeing  that  the 
region  in  question  is  largely  obscured  by  Drift,  and  the  only  places 
where  sections  can  be  observed  are  in  the  various  clay-pits  or  an 
occasional  railway-cutting.  His  paper  is  in  some  sort  a  supplement 
to  the  Sedgwick  Prize  Essay,  which,  though  written  six  or  seven 
years  ago,  has  only  lately  been  published.1  From  this  essay  we 
gather  that,  in  Cambridgeshire  and  the  parts  immediately  adjacent,  it 
is  not  so  difficult  to  trace  the  results  of  the  Corallian  episode  even 
in  the  clays.  In  Lincolnshire,  on  the  other  hand,  muddy  sediments 
appear  to  have  been  deposited  without  a  break,  and  there  are  neither 
limestones  nor  grits  to  help  in  defining  the  horizon. 
The  several  zones  recognized  by  authors  in  the  Oxford  Clay  of 
this  portion  of  England  need  not  detain  us  on  the  present  occasion  : 
it  is  enough  for  our  purpose  that  the  clays  with  Ammonites  of  the 
cordatus-group  are  regarded  as  occupying  the  uppermost  zone. 
1  ‘The  Jurassic  Rocks  of  the  Neighbourhood  of  Cambridge,’ Univ.  Press, 
Camb.  1892. 
i 
VOL.  XLIX. 
