422 STRATIGKAPHICAL GEOLOGY 



3. The Millepore Beds consist of a hard calcareous sandstone 

 with the Bryozoan Haplocecia straminea, overlain by shales and 

 sandstones containing Trigonia reticosta, Ceromya bajociana, 

 Gervillia lata, Pygaster semisulcatus, and other fossils. 



4. The Middle Estuarine Series consists of shales and sandstones, 

 with thin layers of coal varying from 2 to 18 inches in thickness. 

 The "plant bed" of Gristhorpe Bay has yielded fine specimens 

 of ferns (Cladophlebis, Sphenopteris, Tceniopteris, etc.), the cycads 

 Nilssonia and Otozamites, and the horsetail Equisetites columnaris. 



5. The beds termed the Scarborough limestone are grey, shaly 

 limestones, often ferruginous ; they contain Stepheoceras Humphries- 

 ianum, Gervillia acuta, Pseudomonotis braamburiensis, etc. They 

 form a lenticular mass, very thin at Gristhorpe, but thickening to 

 the north-west. 



The Bath Oolites or Bathonian 



Southern Counties. In Dorset and Somerset this stage 

 consists of four distinct members, viz. : 



Feet. 



4. The Cornbrash, rubbly limestones . . 15 to 25 



3. The Forest Marble, flaggy limestones . 80 to 130 



2. The Fuller's Earth, chiefly marly clays . . 150 to 80 

 1. Earthy, oolitic, and shelly limestones . . 6 to 45 



Average about 250 



No. 1 is the zone of Park. ParJcinsoni, and in South Dorset (at 

 Chideock, Burton, Bradstock, and Beaminster) it is only 6 or 7 

 feet thick. Near Crewkerne, however, it has thickened to 12 or 

 15 feet, and near Sherborne the beds vary from 20 to 40 feet. 

 Still farther north at Bruton and Doulting massive beds of oolitic 

 freestone come in, thickening toward the Mendips in contrast to 

 the thinning out of the Inferior Oolite. These beds are quarried for 

 building stone at Doulting, where the following sequence is found 

 below the Fuller's Earth : 



Feet. 



Rubbly and oolitic limestones 10 



Doulting stone, quarried as a freestone . . . .44 

 "Conglomerate Bed," resting on the Upper Liassic clays 1J 



A little farther north in Vallis Vale these beds rest directly on 

 Carboniferous limestone. The basal limestone -conglomerate is 

 correlated by Mr. Buckman with the Upper Trigonia Grit of 

 the Cotteswolds, and the Doulting Beds with the Clypeus Grit. 

 Between them is a break which is filled elsewhere by the " Dundry 



