256 LOWER OOLITIC ROCKS OF ENGLAND : 
Taking Bradford-on-Avon as a central point, we find the Great 
Oolite overlaid by the Bradford Clay, which all observers agree 
in regarding as a subordinate portion of the Forest Marble. 
There the rich beds of Crinoids which flourished on the surface of 
the Great Oolite, indicate some pause in the sedimentary con- 
ditions, and show that in this neighbourhood we have a marked 
divisional plane between the Great Oolite and overlying deposits, 
a boon indeed to those engaged in the process of Geological 
mapping. 
We can trace this horizon of Bradford Clay northwards through 
Box and Corsham, but further on beyond West Keynton and 
Yatton Keynell, the fossiliferous Bradford Clay seems but locally 
developed, and near Cirencester and Kemble it becomes a matter 
of great difficulty to separate the Great Oolite from the Forest 
Marble. There is at any rate wanting in this northerly area, 
evidence of a pause between the Great Oolite and the Forest 
Marble, and Nature has consequently left no definite guide to 
enable us to draw a satisfactory boundary-line. Consequently 
Prof. Hull and Prof. Buckman, in the neighbourhood of Ciren- 
cester, and Phillips and Hull, in Oxfordshire, have differed 
considerably in their interpretation of the sections, differences 
with which I fully sympathize. While Lycett, in reference to 
the Sapperton area, near Stroud, remarks that " probably the 
terms Forest Marble and Bradford Clay might be omitted 
altogether without any detriment to science."* 
Turning to the area south of Bradford-on-Avon, the most 
important evidence is the occurrence of the Bradford Clay in 
Dorsetshire. The characteristic " Bradford Encrinite " has long 
been known from the Forest Marble of that area, but even in 
1884 Damon, referring to the Bradford Clay, observed that "its 
separate occurrence cannot be established in this district [Wey- 
mouth], though its prevailing fossil is sparingly distributed."f 
In Dorsetshire the Forest Marble consists of three main sub- 
divisions, as follows : 
Clay. 
Shelly and oolitic limestone. 
Clay. 
At the base of the lower clay there is a rich fossiliferous bed 
which may be seen at Herbyleigh near Wey mouth, at Burton 
Bradstock, and at Eype near Bridport. Attention was drawn to 
this bed when the Geologists' Association visited Dorsetshire in 
1885, and I then remarked that it appears to represent the Brad- 
ford Clay.J We find the bed to yield numerous Brachiopods, 
large specimens of Rhynchonella various, R. Boueti, Waldheimia 
digona, Terebratula coarctata, also Mytilus pcctinatus, Acrosalcnia, 
&c. 
* The Cotteswold Hills, 1857, p. 142. 
t Geol. Weymouth, &c., 1884-, p. 15. 
J Proc. Geol. Assoc., vol. ix. p. 207. 
