504 
MR.  S.  S.  BTTCKMAH  OX  THE  BAJOCIAH  [HoV.  1 893, 
successive  hemerae,  but  how  they  are  connected  with  the  horizontal 
extension  of  the  strata.  The  following  analysis  will  demonstrate 
these  points. 
In  the  Murchisonce  hemera  the  strata  overstepped  those  of  the 
preceding  hemera,  for  certainly  at  Bradford  Abbas  and  at  Stoford 
the  sequence  leading  up  to  the  strata  of  the  Murchisonce  hemera  is 
not  complete.  The  thickness  of  the  strata  deposited  during  this 
hemera  increases  towards  the  north-east ;  and  the  greatest  thickness 
noted  is  11  feet  at  Marston  Road  Quarry  as  compared  with  less  than 
2  feet  at  Stoford.  In  the  hradfordensis  hemera  the  facts  are  similar. 
In  the  concavi  and  discitce  hemerae  the  maximum  of  deposition 
was  probably  at  Frogden,  or  eastwards  thereof.  Horethorne  Down 
gives  9  feet,  which  seems  to  belong  mostly  to  the  discitce  hemera ; 
but  the  section  is  incomplete.  Frogden  gives  about  12  feet  between 
Lioceras  concavum  and  the  TV itchel lia -beds ;  so  that  perhaps  as  much 
as  15  or  16  feet  of  strata  may  have  been  deposited  in  the  district 
during  these  hemerse. 
During  the  hemera  of  T Vitchellia  sp.,  the  horizontal  area  of 
deposition  appears  to  have  contracted ;  for  the  signs  of  any 
Witchellia-isiUTm,  which  is  shown  to  such  perfection  at  Sandford 
Lane  and  Frogden,  are  of  the  feeblest  in  the  Bradford  area — one 
might  almost  say  there  is  practically  no  sign.  There  was  evidently, 
however,  an  overstep  again  in  the  Sauzei  hemera,  for  the  strata  of 
this  time  are  clearly  shown  as  far  west  as  Stoford.  It  may  be  noted 
that  the  thickest  accumulation  of  deposit  during  the  above  hemerae 
is  about  14  feet  at  Ililborne  Wick — the  most  easterly  point. 
With  the  Humphriesiani  hemera  there  was  again  a  recession, 
for  certainly  Halfway  House  is  the  most  westerly  point  at  which 
the  strata  of  this  time  can  be  properly  identified.  The  same  is  the 
case  with  the  niortensis  hemera.  It  may  be  noted  that  the  deposits 
formed  during  both  these  hemerae  at  Louse  Hill  are  evidently  com¬ 
plete,  and  have  suffered  no  denudation ;  for  there  are  the  two  dis¬ 
tinct  beds  overlain  by  the  band  with  Aulacothyris  4 Meriani ,  var.’ 
It  is  simply  a  case  of  slow  deposition.  At  Sandford  Lane,  however, 
about  2  miles  to  the  east,  it  would  appear  that  any  strata  deposited 
during  the  Humphriesiani  and  niortensis  hemerae  have  been  re¬ 
moved,  some  time  before  the  deposition  of  the  bed  with  Aulaco¬ 
thyris  4  Meriani ,  var/  The  idea  of  removal  is  suggested  by  the  very 
flat  top  of  the  Sandford  Lane  4  Fossil  Bed/  Then  about  j  mile 
to  the  east  the  strata  deposited  during  the  Humphriesiani  and 
niortensis  hemerae  are  preserved,  and  at  Frogden,  1^  mile  distant, 
as  much  as  5  feet  of  very  fossiliferous  strata  was  deposited  during 
these  two  hemerae. 
Was  this  the  locality  of  maximum  deposition  during  these  hemerae  ? 
Looking  at  the  strata  laid  down  during  the  preceding  hemerae,  it 
may  be  seen  that  the  localities  of  maximum  deposits  noted  are  a  few 
miles  eastward  of  the  localities  which  are  most  fossiliferous ;  and 
there  seems  to  have  been  a  gradual  advance  of  the  fossiliferous  area 
eastward.  For  instance,  during  the  concavi  hemera  Bradford 
Abbas  was  certainly  the  headquarters  of  the  mollusca,  and  the 
