cucullata_, &c., appearing in the old brickyard at Arlescot. There is no
other exposure of the seleniferous shales of the zone; their course is
masked by a rich belt of woodland. The natural terraces somewhat
characteristic of this horizon in the midlands are roughly developed
towards the Sun Rising, and are more perfectly shown at Hadsham hollow in
the Hornton vale. At Shenington, four miles southward, there are some
beautifully terraced fields, one locally known as Rattlecombe Slade
recalling to mind the lynchets of the Inferior Oolite sands of
Dorsetshire. They are in the main terraces of drainage, the step-like form
of subsidence being due to the composition of the seleniferous marls and
under waste. The terraces are of exceptional regularity, and run parallel
to the lines of drainage; in one case, however (Kenhill), in the same
locality, they form a bay or recess on the hill slope. A familiar instance
of the last phase is to be seen at the Bear Garden, Banbury. The salient
feature of the Edge Hill escarpment is the Marlstone rock-bed, the
uppermost division of the Middle Lias. Several sections in this zone
(_Ammonites spinatus_) may be seen near the Round House. It has three main
divisions: The upper red layers the roadstone, the middle of several green
hard beds called top-rag, and the lower courses of dark green softer
stone, the best rag (used for building). Some of the quarries have been
worked for centuries, and the grey green slabs of Hornton stone, its local
name, are familiar on the hearths and in the homes of nearly the whole
country-side. At this its N.W. outcrop, the rock thickens considerably,
attaining a development of about twenty-four feet. The stone itself is a
ferruginous limestone, greenish when unweathered, otherwise of a rich red
brown colour. Good evidence of its durability as a building material is
shewn in the fine fourteenth century churches of North Oxon, which are
almost without exception built of the stone. Near the Beacon House on the
Burton Dassett Hills, a good section is exposed in which fossils are found
more freely. Amongst the brachiopod shells _Waldhemia indentata_,
_Terebratula punctata_, _T. Edwardsii_ occur, together with an abundance
of the characteristic _Rhynchonella tetraedra_: _Spiriferinae_ are rare.
When the ironstone workings were extended, ten years or so since, large
_Pholadomya ambigua_ and other shells were obtainable from some sandy beds
at the base of the series. C