Vol. 63.] 



OF THE BATH-DOULTINO DISTEICT. 



423 



beds are absent : the Bathonian rests non-sequentially upon the 

 Toarcian, and in the immediate neighbourhood of the Mendips upon 

 the Palaeozoic rocks (see fig. 4, p. 422). 



In the hills south of the Avon Valley, at Bath, and as far as a 

 line drawn east and west through Carnicote, near Timsbury, the 

 Upper Trigonia-Grit rests upon the Midford Sands. South of this 

 line, and between it and one similarly oriented about half a mile 

 farther south, it rests upon the local Cephalopod-Bed — here of 

 greater antiquity than the ' Sands' (Midford); not younger, as in the 

 case of the Cotteswold Cephalopod-Bed. South of the latter line, the 

 Upper Trigonia-Giit, often conglomeratic, rests upon the non-arena- 

 ceous Liassic deposits, until, in the more immediate neighbourhood 

 of the Mendip Hills, it is overstepped by the Doulting Stone, which 

 rests directly upon the well-planed, bored, and oyster-covered surface 

 of the White Lias (Rhsetic) and the Carboniferous Limestone. 



On the south side of the Mendips, in the neighbourhood of 

 Doulting, the Upper Trigonia-Qiit comes in again, and is seen 

 in the railway-cutting near that village. 



The Fullers' Earth at Midford, at least the basal portion, is of 

 zigzag hemera. Therefore the Inferior Oolite between it and the 

 Upper Trigonia-Giit must be of post-Garantiance, ^iQ-zigzag date. 

 This intervening deposit (where fully-developed) admits of sub- 

 division into five parts, in descending order : Rubbly Beds, Ana- 

 ftacm-Limestones, Doulting Stone, Upper Coral-Bed, and Dundry 

 Freestone. The Upper Coral-Bed is of Truellii hemera, and a por- 

 tion or the whole of the Doulting Stone may be so as well ; but, for 

 the present, the Doulting Beds (that is, the Rubbly Beds, Anabacia- 

 Limestones, and Doulting Stone) are best regarded as of inter- 

 Truellii-zigzag date; and the Dundry Freestone as of inter- Garan- 

 tiance-Truellii date. 



In an Appendix (p. 424), Mr. S. S. Buckman has correlated 

 these beds with those in Dorset, and in a future paper I purpose 

 to deal with their equivalents in the South Cotteswolds. 



In another Appendix (p. 426), the late Mr. J. F. Walker and I 

 have dealt with the Brachiopoda from the Fullers' Earth, and have 

 named several new species. Below are added figures of Ostrea Knorri: 

 a form that does not seem to have often received its correct name 

 in this country. 



Fig. 5. — Ostrea Knorri, Voltz. 



