EASTERN BRITISH PLIOCENES. 301
Here the fauna, taken as a whole, is different to that met
with in the older Crags—northern forms predominating. Of
the 200 shells that are known from this area about ten per cent,
are either extinct, survivors of the earlier fauna, or of unknown
habitat. A notable feature of this zone is the number of still
living land and freshwater species it has yielded, intermixed
with marine shells whose living habitat is in different bathy-
metrical horizons and world-distribution. I may refer to my
paper for fuller particulars, both as to nature of the deposits
at Butley and their contents.
I formerly grouped the Norwich Crag with the preceding
Upper or Butley Crag, as they appeared to pass imperceptibly
into each other, the two never being superimposed, treating the
Norwich Crag as a shallower or perhaps estuarine deposit, the
distortion incidental to the bulk of the ordinary Periwinkles
(Littorina rudis and L. littorea) suggesting the influence of fresh
water in the sea or estuary. This horizon, the Icenian,
is now known to be newer and quite distinct. It was de-
posited in a shallow sea, the bed of which gradually subsiding,
the deposit having been found by boring to be some hundreds
of feet in thickness, although its Mollusca throughout are of the
same shallow water character. For the extension of the sea
eastwards, I must refer to some maps published in Mr. Harmer's
papers. A fairly considerable fauna is given by Mr. S. P.
Woodward as pertaining to this horizon, in Gunn's Geology of
Norfolk. Aldeby near Beccles, Thorpe near Aldborough, and
probably Sudbourne Church walks may be added to the fossili-
ferous localities of this stage.
Dr. Crowfoot has kindly given me permission to add a list
of the species found in a dark sandy silt of Icenian (Norwich
Crag) age, when sinking a well at Beccles. In his collection I
found some interesting forms new to the Crag Seas.
Pisidium supinum Anomia ephippium
Vallonia excentrica Astarte compressa var. striata
Hydrobia ulvae Cardita chamaeformis
,, ventrosa Cardium edule
Cadulus (gadus) Circe minima
Cerithium tricinctum Corbula gibba
Chemnitzia plicatula Leda (Yoldia) limatula
,, internodula Lucina borealis
Eulimella nitidissima „ divaricata