416 
THE CRETACEOUS ROCKS OF BRITAIN. 
base of the zone of H. 'planus should, in their opinion, lie taken at 
the layer of flints which there occurs 15 feet above the double layer 
of green-coated nodules. 
Since the above was written, Dr. Bowes description of the 
Dorset coast sections has been published,* and I have availed 
myself of the information it contains. 
Stratigraphical Details. 
A complete section of the Middle Chalk is furnished bv Ballard 
cliff, north of Swanage. Combining the accounts of this given by 
Professor Barrois in 1876 and by Mr. Stralian in 1898 the succes¬ 
sion appears to be as follows : — 
feet 
Upper Chalk , with many Hints (see Volume III.). 
Chalk without Hints, massive but somewhat lumpy, 
with a layer of hard green-coated nodules at the 
base ------- about 20 
Terebra- 
tulina 
Zone 
Zone of 
Rh. 
Cuvieri. 
Hard rough and lumpy chalk ----- 
Smooth thick-bedded chalk, with partings of marl - 
Rough chalk, becoming nodular below - - - 
Rough, nodular and flaky chalk, with sparry joints 
(Melbourn Rock) ------- 
Smooth compact chalk in thin beds with marly 
partings - - 
6 
60 
30 
6 
12S 
The Melbourn Hock still forms a well-marked band near the base 
and from the chalk which overlies it Mi*. Bliodes obtained the usual 
fossils of the Rhynchonellu Cuvieri zone, the only species of 
special interest being Ammonites Cunningtoni. The section is often 
partially obscured by falls and slips, so that it is difficult to mea¬ 
sure it or to collect from it in detail. Mi’. Bliodes found Tere- 
bratulina gracilis var. lata fairly abundant in the upper 20 feet 
of chalk below the green-coated nodules, while Hoi aster planus 
was common above that layer and in a band of rough chalk with 
sponge remains. At the top of the rough nodular chalk he found 
Micraster corbovis, Ter. gracilis var. lata and Porosphcera globularis f, 
and he did not find any Micrasters below this horizon. 
Of this locality Dr. Bowe writes:—“We landed near Ballard 
Point on the T. gracilis beds and found a wonderfully air- 
weathered section. The double band of yellow-green nodules 
. . . is here well developed and is, as in all other sections on 
this coast, well doAvn in the T. gracilis zone. This cliff-face was 
studded with fossils and it is the only exposure in this zone which 
yielded a good list. We obtained on this small face thirty-five 
species.” Among those mentioned are Gidaris serrifera , Penta- 
crinus Agassizi , Hemiaster minimus, Holster 'planus, Inoc- 
eramus Cuvieri, Turbo gemmatus and the Bryozoa Homceosolen 
ramulosum and Diastopora oceani. 
* Proc. Geol. Assoc. Vol. xvii., p. 1 (1901). 
t In the Memoir on the Isle of Pur beck (p. 171) these fossils were by 
mistake included in the list of those from the beds below the green nodules. 
