Yol.  49.] 
OF  THE  SHERBOEHE  DISTRICT. 
481 
some  modification  adopted,  if  the  true  fannal  sequence  is  to  be 
expressed  with  that  accuracy  which  is  now  necessary.  Thus,  in 
1887,  Hudleston,  in  his  very  able  survey  of  the  Inferior  Oolite,1 
although  he  adopted  the  zonal  divisions  which  I  had  briefly  sketched 
out  in  1881, 2  showed  plainly  that  the  strata  required  more  sub¬ 
division  ;  and  this  subdivision  he  accomplished  by  the  term  ‘  beds/ 
and  by  designatory  letters.  In  dealing  with  the  Toarcian  I  have 
shown  the  necessity,  for  the  purposes  of  correlation,  of  adopting 
greater  accuracy  in  division  than  the  existing  zones  allowed ;  and 
for  my  subdivisions  I  used  the  term  4  beds/  Quite  recently,  in 
communications  to  the  Geological  Society  of  France,  Munier- 
Chalmas  3  and  Haug 4  have  shown  the  geological  value  of  small 
divisions.  The  work  of  the  former  in  Normandy  is  most  valuable 
for  its  exactness ;  in  comparison,  our  researches  on  this  side  of  the 
Channel  are  still  much  behindhand. 
To  such  subdivisions,  however,  H.  B.  Woodward  5  is  opposed;  but 
then  he  is  not  looking  at  the  matter  from  a  biological  point  of  view. 
For  correlation  in  certain  cases  fewer  zones  may  be  used;  but  any 
such  correlation  is  deficient  in  the  precision  which  the  biological 
palaeontologist  demands,  and  fossils  labelled  on  such  a  plan  are  useless 
to  him.  In  this  connexion  it  may  be  remarked  that  the  more  minute 
the  correlation  the  better  for  the  student :  he  can  easily  dispense 
with  detail ;  but  if  such  detail  as  he  does  need  be  not  given  in  any 
paper,  he  searches  in  vain  for  information. 
The  term  ‘  zone ’  is  said  to  be  used  in  geology  in  a  zoological  sense  ; 
but  in  zoology  it  is  really  used  in  a  different  sense.  However,  I  take 
it  that  of  late  years  the  stratum  (or  strata)  characterized  by  an 
assemblage  of  organic  remains,  more  or  less  peculiar  thereto,  has 
been  regarded  as  a  zone;  and,  as  H.  B.  Woodward  practically  im¬ 
plies,  though  his  definition  of  a  zone  is  faulty,6  the  presence  of  any 
of  the  species  known  to  be  sufficiently  peculiar  to  a  given  horizon 
is  considered  to  denote  the  zone  in  localities  from  which  the 
index-species  is  absent.  This  may  be  called  the  geologist’s  zoological 
use  of  the  term.  Charles  Moore 7  seems  to  have  been  the  only  one 
to  use  the  term  in  a  strictly  palaeontological  sense  :  he  confined  it  to 
the  exact  horizon  of  a  particular  fossil. 
The  term  6  Hemera .’ — It  is  for  a  palaeontological  purpose  similar 
to  Moore’s  use  of  £  zone  ’  that  I  propose  the  term  ‘  hemera  ’  (rj/jtepa).8 
Its  meaning  is  c  day,’  or  ‘  time  ;  ’  and  I  wish  to  use  it  as  the  chro¬ 
nological  indicator  of  the  faunal  sequence.  Successive  ‘  hemerae  ’ 
1  ‘British  Jurassic  Gasteropoda/  Palasontograph.  Soc.  1887,  No.  i.  pt.  1. 
2  *  Ammonites  from  the  Inferior  Oolite/  Quart.  Journ.  Geol.  Soc.  vol.  xxxvii. 
p.  588. 
3  Compte-rendu  sommaire  des  Seances,  No.  14,  p.  164,  1892. 
4  Ibid.  p.  174. 
0  ‘  On  Geological  Zones/  Proc.  Geol.  Assoc,  vol.  xii.  (1892)  p.  295. 
6  Ibid.  p.  298. 
7  Proc.  Somerset  Archseol.  Soc.  vol.  xiii.  1865-6. 
8  [Originally  the  word  ‘  emar  ’  (ijpap — the  Homeric  form  of  rjp,epa)  was 
chosen ;  but  in  deference  to  the  wish  expressed  by  the  Council  of  the  Geological 
Society  I  have  substituted  the  term  ‘  hemera/ — July  5th,  1893.] 
2k  2 
