Prof. S. H. Reynolds—The Rocks of the Avon Section. 543 
to belong to S. Morrisiana King, a species which is rather common at 
Thickley. 
I shall not in this short note attempt to give a complete list of 
the rather numerous fossils that occur at Thickley, as | am preparing 
a synoptical table of the fauna of the chief fossiliferous horizons of 
the Durham Permian for a future paper. The difficult group of the 
Permain Strophalosias of England is one on which much might be 
written, including among them the curious small form called by 
King S. parva, which domiciles itself in the interior of empty valves 
of Productus horridus in the Shell Limestone reef. A sound revision 
of the Permian fauna is a task which would undoubtedly repay 
the effort expended on it. 
EXPLANATION OF PLATE XII. 
Surface of a block of Caleareous Lower Magnesian Limestone from East 
Thickley Quarry, Durham, about § natural size. In middle Productus 
horridus Sow., with long spines. At A, a Strophalosia goldfussi Miinst. 
attached to the Productws spines; BBB, specimens of Streptorhynchus 
pelargonatus Schloth. ; C, specimen of Spirifer alata Schloth. 
On the Rocks of the Avon Section, Clifton. 
By Sipney H. Rerynoups, M.A., Se.D. 
Ay account of the lithological succession of the rocks of the 
Avon Gorge was given at the Bournemouth meeting of the 
British Association in 1919, and a summary of the rock-characters 
mainly from the lithological aspect was published in the 
GroLogicaL MaGazine (1919, p. 523). Further work has now 
been done, and a full account of the rocks is published in the .- 
current issue of the Quarterly Journal of the Geological Society. 
The following summary prepared for the above paper was con- 
sidered redundant owing to the fact that the matter it contains 
is already incorporated in the text of the paper. In view, how- — 
ever, of the importance and accessibility of the Avon Section it 
is thought that a brief statement such as the following, in which 
the rock-characters are summarized firstly from a stratigraphical 
and secondly from a lithological aspect may be useful. 
I. DeEscrIPTION OF THE ROCKS FROM THE STRATIGRAPHICAL 
ASPECT. 
A. The Cleistopora Beds. 
The Modiola Shales K,,.—The lower beds, which are ill-exposed, 
consist of sandy shales, of tencalcareous, and impure limestone. 
The upper beds consist of thin-bedded, often sandy, and rubbly 
limestones with reddish shaly partings. Small lamellibranchs, 
ostracods, and calcareous alge are the most characteristic 
organisms. Small gastropods, brachiopods, and crinoids are also 
1 Quart. Journ. Geol. Soc., vol. Ixxvii, 1921, p. 213. 
