256 A. J. Jukes-Browne—The Subdivisions of the Chalk. 
because it clearly forms the basement bed of the Lower Chalk. 
Between this, however, and the overlying bed of grey sandy stone 
there is a clear line of separation, and the latter is perhaps more 
likely to be the attenuated representative of the Totternhoe Stone, 
than of the Chalk Marl. The occurrence of Ammonites rhothomagensis, 
Pecten Beaveri, Discoidea cylindrica, and Epiaster crassisimus is at 
any rate suggestive of a higher horizon than that which is generally 
characterized by Plocoscyphia meandrina, with which they are here 
associated. 
The succeeding beds, E., F., G., of Barrois, are doubtless homotaxial 
with the zone of Holaster subglobosus when used in its more limited 
sense, and as I have already defined it. 
The remaining 12 or 15 feet at the top of the cliff at Hunstanton 
are referred by Barrois to his zone d Belenmites plenus. This, how- 
ever, is a somewhat ambiguous term, because he uses it also for 
the marly layer at Cherry Hinton, which is really the base of the 
Melbourn Rock, and above the true zone of Bel. plenus. It was 
with the latter, which has a greater development in the north of 
France, that Barrois probably intended to compare this portion of the 
Norfolk Chalk. 
The Hunstanton section is therefore cut off at a very interesting 
point, just before the top of the Lower Chalk is reached. Dr. 
Barrois, however, indicates the outcrop of the® overlying zone at 
Sherborne in these words—‘“To the north of the village, in the 
higher part of the quarries, I recognized the hard nodular bed which 
occurs throughout England towards the base of the zone of Inocer- 
amus labiatus.” Can this be the Melbourn Rock? is the comment 
immediately suggested by this description. The nodular chalk to 
which Barrois refers as occurring throughout (the south of) England 
is probably rather above the base of the zone, but it would be very 
interesting to determine whether the Sherborne bed may not be the 
actual representative of the Melbourn Rock, because it would then 
supply the desideratum of a base-line for the middle division of the 
Chalk in Norfolk. 
It is very probable that the hard chalk of Sharbome with 
Inoceramus labiatus and Rhynchonella Cuviert formed part of Wood- 
ward’s ‘‘ Lower or Hard Chalk,” and that his Medial Chalk was 
merely intended to signify that portion which contains a few flints, 
and is intermediate between that without any and that with many 
flints. The localities given by Woodward appear to be chiefly along 
a line which would correspond with the outcrop of Barrois’ zone of 
Holaster planus ; a zone which seems to have a considerable thick- 
ness in Norfolk, and to contain grey instead of black flints. Now, 
however, it has become necessary that the Medial Chalk should 
receive a more strict definition, and it seems desirable to extend the 
application of the term rather beyond its original scope, so as to 
bring the Norfolk divisions into correspondence with those now. 
proposed for the rest of England. 
I would therefore suggest that Norfolk geologists should take 
every opportunity of searching for the representatives of the two 
