MIDDLE CHALK—KENT. 
375 
Cliff and on the east of Dover. Another frequent and character¬ 
istic fossil is Inoceramus Cuvieri, and in the upper beds Micraster 
corbovis and Holaster planus are not rare. 
The first layer of flints occurs about 60 feet above the bed taken 
as the base of the zone, and very little more of the chalk can be 
reached by Shakespeare’s Cliff, but above the entrance to the 
tunnel at Haycliff there is about 20 feet of chalk above this line 
of flints, and we believe that the chalk exposed above the beach at 
the eastern end of the town of Dover is very little, if at all, above that 
which forms the top of the cliff above the Haycliff Tunnel. 
Near the base of this eastern cliff two well-marked seams of grey 
marl may be seen, the upper one containing some fossils and small 
embedded pebbles of chalk. About 16 feet above these is a layer 
of flints, succeded by about 30 feet of chalk, in which there are 
two discontinuous layers or lines of flints. Above this come two 
well-marked layers of argillaceous marl, separated by a bed 
of somewhat nodular chalk, with irregular greyish veinings 4 feet 
thick. In these beds Terebratulina gracilis var. lata, Rhynchonella 
Cuvieri, and Inoceramus mytiloides are common. 
The upper layer of marl is succeeded by about 15 feet of whitish 
chalk with grey veinings, and near the top of this are two con¬ 
spicuous layers of flints about 3 feet apart. Then comes another 
layer of grey marl, which is the bed taken by Phillips as the limit 
between his “ chalk with few flints ” and the “ chalk with many 
flints ”; this layer, too, was afterwards taken by one of us as the 
summit of the Terebratulina zone.* Now, however, we prefer 
to carry this zone about 16 feet higher up ; the chalk above this 
marl band is soft and whitish, but it includes lumps of very hard 
crystalline chalk, which near the top become numerous, and have 
a tendency to arrangement in layers. This chalk contains some 
specimens of Holaster planus. It is succeeded by a bed about 4 feet 
thick, which is full of flints, and this we take as the base of the 
Upper Chalk. (See Fig. 68.) 
Since the above was written Dr. Rowe has published an account 
of the Dover cliffs, with especial reference to the zonal distribution 
of the fossils, f His measurements of the distances between the 
marl-bands in the east cliff agree very nearly with ours, but he 
takes the upper limit of the zone at a seam of marl which is about 
7 feet above the plane which we regard as the base of the zone of 
Holaster planus. The fact appears to be that the change from the 
fauna of one zone to that of the other takes place in this 7 feet of 
chalk ; Holaster planus is fairly common in it, and though Micros - 
ters are rare and Echinocorys does not seem to occur, we prefer 
to take the flint-bed as the top of the zone, because a similar but 
rather thinner bed of flints occurs in the inland sections, while the 
marl band is not recognisable inland. 
* W. Hill in Quart. Journ. Geol. Soc., Vol. xlii., p. 235 (188ft). 
t Proc. Geol. Assoc., Vol. xvi., p. 289 (1900). 
