Duston,  within  a  distance  of  a  mile  and  a  half,  they  present  t
section  of  25  feet  They  here  consist  of  a  dark  red  brown  rock,
having  a  cellular  texture  (the  walls  of  rich  iron  ore  enclosing
ochreous  cores),  and  are  disposed  in  some  seven  or  eight  beds,  from
three  to  five  feet  in  thickness,  divided  by  joints  and  fissures,  and
traversed  by  shelly  and  coral  zones,  and  a  plant-bed.  Near  the
top  is  a  zone  crowded  with  Astarte  eXegann,  associated  with
which  occur  patclies  of  Astarte  minima ;  this  zone  is  persistent  over
a  considerable  area,  and  is  useful  in  determining  at  other  points  the
general  sequence  and  position  of  certain  beds.  The  fossils  are
generally  characteristic  Inferior  Oolite  forms  ;  but  with  them  ii
found  Pholadomya  amhigua  (?)  and  from  near  the  bottom  of  the  seriei
have  been  obtained,  from  widely -separated  localities,  two  "well-defined
examples  of  Ammonites  hifrons.  This  leads  me  to  conjecture  that,
in  the  lowest  portion  of  the  Ironstone -beds  of  the  Northampton
Sand,  we  have  a  passage-bed  from  the  Upper  Lias  to  the  Inferior
Oolite,  representing,  perhaps,  the  Cephaloi)oda-bed  of  the  Cotswold
Hills  and  the  sands  below.  The  Pal  aeon  tological  evidence,  I  think,
proves  conclusively  that  the  Northamptonshire  ironstone  (all  below
the  coarse  shelly  limestone  No.  5,  and  the  slate-bed  No.  6,  and
including  these  beds,  down  to  the  Upper  Lias  Clay)  is  Liferior
Oolite.
