442 Mark W. Norman — The Loiver Cretaceous Beds, 



is called the " Black Band." Besting on it is a layer of Rag, with 

 a bed of soft sandstone of a light grey colour, sparsely fossiliferous ; 

 succeeded by another bed of Kag of one foot, which rests upon a 

 band of light grey sandstone of about four feet thick ; it contains no 

 fossils except large groups of semi-silicified sponge-like bodies. 



Another bed of hard blue Eag one foot thick succeeds this, upon 

 which is deposited a thick bed of close-grained grey sandstone of 

 great economic importance, being in much requisition for building 

 purposes, which, with a soft bed of the same material on the top, is 

 about five feet thick. It is locally termed the " freestone bed," and 

 is more compact and harder than the beds below it. This bed is 

 quarried and sawn into blocks for quoins, etc., of buildings, and is 

 conspicuous for its thickness compared with the other beds along 

 the face of the cliffs which form the great wall of the Undercliff 

 between Ventnor and Blackgang. It is from about 32 feet to 34 feet 

 below the Lower Chalk. 



Next in ascending order is an upper bed of Eag one foot thick, on 

 which rests the so-called " Firestone " bed (by which JJr. Mantell 

 proposed to name the whole of the deposits) ; which is after all but 

 a very subordinate member of the group, consisting merely of a bed 

 of hard laminated sandstone, from 8 ins. to 9 ins. thick ; and a layer 

 of Eag 9 ins. thick, succeeded by an upper bed of the same litho- 

 logical character ; the whole averaging about two feet in thickness. 

 "J'his bed was locally called " Firestone " by the old inhabitants of 

 the Undercliff, and used as a substitute for bricks for fire-places and 

 the bottoms of ovens. 



Third Division ( Chert Beds) . 



This division consists of from twenty to twenty-four beds of chert 

 and laminated siliceous sandstone alternating with each other and 

 very unevenly bedded throughout, some of the beds varying in 

 tliickness from a few inches to two feet; the seams of the sandstone 

 being interstratified with large concretions of Eag, in the same line 

 of bedding. The layers of sandstone vary much in thickness. 



This division also contains three or four beds of black and dark 

 grey flinty chert, the lowermost of which is about two feet thick, and 

 called by Dr. Mantell " coarse chalcedony." The upper beds are 

 crowded with spicula of sponges. 



Besides these, there are several thin bands of white brittle chert, 

 apparently siliceous, and breaking into square fragments. 



This series of deposits is very sparsely fossiliferous, the fossils 

 being chiefly derived. Some of the laj'ers contain comminuted 

 shells with single waterworn valves of Ostrea conica, etc. 



I have upon two or three occasions discovered a large Nautilus in 

 the upper beds of this series of deposits, the chambers of which were 

 filled with a dark blue chalcedony. 



Fourth Division (Chloritic Marl, etc.). 



Deposited upon a seam of irregular-bedded Rag, being the top- 

 most layer of the chert beds, is a layer of laminated pea-green sand, 



