522 
TELE  BAJOCIAX  OF  THE  SHETBORXE  DISTRICT.  [NoV.  1 893, 
It  was  obvious  to  those  acquainted  with  the  Inferior  Oolite  of 
North  Dorset  that  the  deposits,  as  a  rule,  thickened  to  the  eastward, 
and  when  this  occurred  they  frequently  became  less  valuable  to  the 
collector.  He  had  not  noticed  that  this  was  reversed  in  the  very 
highest  beds. 
I  he  great  value  of  such  work  as  that  contained  in  the  paper  lay 
in  the  fact  that  it  allowed  a  close  correlation  of  deposits  in  different 
districts  to  be  made,  and  he  had  little  doubt  that  Mr.  Buc-kman’s 
paper  would  be  of  assistance  to  those  who  were  studying  the  Jurassic 
deposits  in  detail  in  other  countries. 
Prof.  Blake  considered  the  paper  a  very  interesting  one  from  a 
palaeontological  point  of  view.  The  development  and  succession  of 
any  single  group  of  organisms,  whether  Ammonites  or  Graptolites, 
could  scarcely  be  traced  too  minutely  ;  and,  so  far  as  the  succession 
of  forms  in  different  districts  coincided,  it  showed  that  the  develop¬ 
ment  of  the  group  took  place  upon  lines  which  were  independent  of 
the  environment,  and  this  had  a  biological  significance.  But  from 
a  stratigraphical  point  of  view  we  had  no  reason  to  conclude  that 
corresponding  stages  in  different  areas  were  synchronous,  nor  could 
he  imagine  it  possible  that  divisions  of  this  kind  could  be  traced  in 
the  Midland  counties  or  in  Yorkshire.  He  called  attention  to  the 
fact  that,  though  Ammonites  bradfordensis  was  a  large  form  and 
A.  Humphriesianus  a  still  larger  one,  their  zones  or  ‘  emata  ’  in 
some  of  the  sections  were  represented  as  1  in.  and  3  in.  respectively; 
so  that  any  single  specimen  of  such  an  Ammonite  would  have  some 
difficulty  in  getting  into  its  own  zone — in  fact,  we  should  have  to 
draw  geological  lines,  not  only  in  the  middle  of  a  band  of  limestone, 
but  in  the  middle  of  a  fossil.  He  pointed  out  also  that  several  of 
these  4  emata  ’  were  unrepresented  in  the  different  quarries,  and 
enquired  whether  such  a  circumstance  indicated  an  unconformity  or 
not,  for  these  cases  seem  very  numerous  in  deposits  over  an  area 
said  to  be  less  than  7  miles  square  and  of  average  thickness  about 
90  feet. 
The  Bev.  H.  H.  'VTixwood  regretted  the  absence  of  the  Author  of 
the  paper,  whose  accurate  and  painstaking  work  in  the  Sherborne 
district  and  elsewhere  was  so  well  known  to  geologists.  He  wanted 
to  know  why  so  many  foreign  terms  were  used  when  English  ones 
would  answer  the  purpose  as  well ;  and  he  hoped  that  the  President 
would  not  endorse  with  his  approval  the  introduction  of  the  words 
‘  emar  ’  and  4  emata.’  If  Mr.  Buckman  found  it  necessary  to 
subdivide  his  zones  in  that  typical  district,  might  not  ‘horizon’ 
or  ‘  sub-zone  ’  answer  his  purpose  equally  well  ? 
Mr.  Mare  also  spoke. 
