Tol.  49. _  AXXIVEESAET  ADDEESS  OE  THE  PEESZDEXT.  12 9 
It  seems  to  have  made  no  difference  to  an  Ammonite  whether  lie 
was  buried  in  clay,  sand,  or  calcareous  debris,  and  this  fact  is 
very  strongly  brought  out  by  Mr.  Buc-kman’s  researches  on  the 
Ammonites  of  the  border-zones  of  Lias  and  Oolite.  At  the  same 
time,  one  must  admit  that  the  system  of  zonal  classification  by 
means  of  Ammonites  has,  in  some  instances,  been  carried  to  excess. 
It  is  quite  possible,  for  instance,  that  in  the  case  of  the  old 
Gloucestershire  Cephalopoda-bed  and  its  associated  sands  there  may 
have  been  a  little  too  much  subdivision :  at  least  some  of  the 
so-called  zones  might  be  viewed  as  sub-zones.  Mo  doubt  these 
names  are  a. terrible  tax  upon  the  memory,  especially  when  the 
evolution  of  Ammonite-genera  proceeds  at  its  present  rapid  pace. 
Lurthermore,  it  must  be  admitted  that  zones  in  some  cases  blend 
both  laterally  and  vertically,  and  it  is  quite  possible  that  the 
Ammonites  eponymiis,  or  name-giving  species,  may  occasionally  be 
found  straying  within  the  jurisdiction  of  another  chief. 
These  and  similar  points  are  sure  to  be  urged  by  any  one  who  is 
desirous  of  taking  an  ex  parte  view  of  any  particular  case  ;  but, 
when  all  demurrers  have  been  duly  considered,  there  remains  a 
considerable  balance  of  evidence  in  support  of  the  chronological 
value  of  Ammonite-zones.  In  the  case  before  us,  unless  we  dispute 
Mr.  Buckman’s  facts,  certain  Ammonite-forms  are  observed  to 
occupy  definite  relative  positions  over  a  considerable  area.  It 
seems  quite  in  accordance  with  the  maxims  of  stratigraphical 
palseontology  to  believe  that  each  of  these  forms,  or  rather  group 
of  forms,  was  fairly  synchronous  over  the  area,  and  that,  if  we 
wish  to  know  the  age  of  any  particular  bed  in  the  series,  we  must 
rely  upon  the  Ammonites  and  not  upon  the  lithology. 
These  considerations  introduce  a  still  larger  question,  viz.  as  to 
where  the  boundary  between  the  Lias  and  the  Oolites  should  be 
drawn.  In  this  connexion  I  will  not  discuss  Mr.  Buekman’s 
suggestion  to  take  the  reign  of  the  Hildoceraticke  as  indicating  an 
intermediate  series,  which  is  to  include  the  Upper  Lias  and  the 
Lower  Division  of  the  Inferior  Oolite  under  the  name  of  4  Toarcian.’ 
On  purely  palaeontological  grounds  something  may  be  said  for  this 
arrangement  in  those  districts,  such  as  Dorsetshire,  where  a 
Cephalopod  facies  predominates:  but  throughout  the  greater  part 
of  England  it  would  not  work  at  all.  Of  course,  this  is  to  a  certain 
extent  an  old  controversy,  but  we  must  not  forget  that  the  original 
divisions  were  made  in  England,  nor  is  it  likely  that  they  will  be 
altered  to  suit  conditions  which  prevail  in  districts  far  removed 
from  the  type-area. 
