108 THE CRETACEOUS ROCKS OF BRITAIN. 
ft. 
Soil and rubble * l 
Greyish-white blocky chalk, breaking into loose angular 
blocks - -- -- -- -- -- is 
Softer silty chalk, containing many lumps of hard chalk ; seen 
for ----------- 3 
Am. [Acanth.] Mantelli occurred throughout; the lowest bed 
yielded Scaphites cequalis, Turrilites sp., Pecten orbicularis, Ino- 
ceramus latus, d’Orb, Ostrea sp., and Terebratula semiglobosa. 
This pit may be 20 feet above the base of the Chalk. 
Beyond this point the hard lumps seem to die out, and the lower 
20 feet of the chalk consists entirely of soft silty chalk, breaking 
into blocks, and only occasionally containing seams of still softer 
laminated chalk. Thus half a mile north of Melcombe Horsey 
a pit at Melcombe Park Dairy shows about 14 feet of blocky chalk, 
softer in the lower half, and without any hard lumps. By digging 
alongside the farm buildings, Mr. Hill found that the same soft chalk 
continued to the farm gates, close to which the glauconitic basement 
bed w r as seen. Sections a little farther west show that the total 
thickness of the Lower Chalk is here reduced to 100 feet. 
Thus in a distance of less than ten miles this division has thinned 
from 180 to 100 feet. We think that the lowest beds of the Mel- 
bury section, i.e., the zone of Stauronema Garteri and the lower 
part of the Chalk Marl, have disappeared entirely, and that the 
change in the character of the beds is due to lack of the argillaceous 
material present in ordinary Chalk Marl. Near Anstey the zone of 
Ammonites varians is probably not more than 30 feet thick, and 
there are decided signs of erosion at its base. 
In the Dorchester Museum there are a number of fossils from the 
Lower Chalk of Stoke Wake (obtained many years ago from quarries 
now overgrown) and from near Armswell, a hamlet west of Anstey. 
Most, if not all, of these must have come from the lowest beds 
(zone of Am. varians). The following is a list of them : — 
Ammonites [Acanth.] Mantelli, Sow. 
„ [ „ ] rotomagensis, d'Orb. 
„ [ ] sussexiensis, Mant. 
„ [Schloenb.] varians, Sow. 
„ [ „ ] Coupei, Brongn. 
Scaphites aequalis, Soiv. 
Baculites baculoides ? d’Orb. 
Turrilites costatus, Sow. 
Nautilus expansus, Sou. 
„ deslongchampsianus, d'Orb. 
Inoceramus latus, d'Orb. non 
Lima globosa. Sow. [Mant. 
Pecten Beaveri, Sow. 
„ fissicosta 1 Eth. 
„ orbicularis, Sow. 
„ (Neithea)5-costatus,£W;. 
Ostrea vesicularis, Lam. 
Terebratula semiglobosa, Sow. 
Terebiatulina striata, Wahl. 
Rhynchonella grasiana, d'Orb. 
Zone of Holaster Subglobosus. 
Under this head we shall mention those sections which expose the 
uppermost portion of the Lower Chalk. The first of these is the 
large quarry previously mentioned on the western slope of Melbury 
Hill, south of Shaftesbury. The highest part of this shows massive 
greyish-white chalk and three or four feet of grey shaly marl,overlain 
by Melbourn Rock. 
