2/4 JURASSIC. 



observed that A. capricornus ranges upwards into the zone of A. 

 margaritatus. In this area the Marlstone, which is a hard grey lime- 

 stone, is so full of specimens of Rhyjichondla tetrahcdra as to con- 

 stitute a Rhynchonella-bed. According to the Rev. J. E. Cross, 

 Anuiiotiites spinatus occurs in the lower part of it, and A. serpent intis 

 and A. coinmimis in the upper part. This case is somewhat similar 

 to that on the Dorsetshire coast.' (See p. 271.) 



In Yorkshire the INIiddle Lias comprises the i^ollowing beds : — 



2. Ironstone series. (Kettleness Beds.-) 

 I. Sandy series. (Staithes Beds.-) 



As remarked by Messrs. Tate and Blake, the term IMarlstone has 

 been variously applied in Yorkshire, and is sometimes taken to 

 include all the beds to the base of the zone of Anwioniles fuargari- 

 tatus.^ The beds are shown in the cliffs of Staithes Nab and 

 Kettleness, between Redcar and Whitby, and again south of 

 Whitby, between Saltwick Nab and Blue Wyke Point. 



The Sandy Series (Marlstone of John Phillips), with A. margari- 

 tatus, is shown at Hummersea (100 feet), Huntcliff, etc., and is 

 composed of beds of sandstone, shales, and clay-ironstone. Among 

 the fossils it is noteworthy that very small specimens of Ammonites 

 capricornus occur. Protocardiurn truncation is an abundant form. 

 The upper portion of the Middle Lias, which belongs mainly to 

 the zone oi Ammonites spinatus, consists of argillaceous shales with, 

 locally, bands of ironstone, twenty to forty feet in thickness. Two 

 prominent beds are the Cleveland main seam, and the Bottom 

 seam, but other layers are known in places, as at Skelton Beck. 

 This division includes the Grosmont series, near Whitby, and the 

 Hawsker Beds of the cliffs of Hawsker Bottom, south of Whitby. 

 In the main seam there occur A. spinatus, Terebratula punctata, 

 Rhynchonella tetrahcdra, etc. Trigonia Lingnnensis also occurs in 

 the ironstone, and this species has been met with in the Middle 

 Lias of Northamptonshire. 



Economic products, etc., of the Middle Lias. 



The Cleveland Iron-ore is well known ; it is derived from the upper part of the 

 Middle Lias of the Cleveland Hills east of Northallerton in Yorkshire, and was 

 first worked in 1848. The ore occurs in several seams, but the main bed of iron- 

 stone is from 12 to nearly 20 feet in tliickness. The beds worked extend inland from 

 near Redcar to Eston Nab, near Middlesborough-on-Tees. There are mines at 

 Upleatham, Hummersea, Rockcliff, Kettleness, etc. The ore is an impure 

 carbonate, it is a bluish or greenish-grey oolitic ironstone, the colour being derived 

 in part from silicate of iron, and it is highly fossiliferous. It yields about 30 per 

 cent, of metallic iron. Pecten cequivalvis occurs in the main seam, which is called 



1 Q.J. xxxi. 120. 



' Young and Bird, Geol. Survey of the Yorkshire Coast, 1822. 



^ Yorkshire Lias, p. 104 ; see also Phillips, Q. J. xiv. 96 ; Explan. Sheets, 

 93 N.E., 95 N.W., and 96 N.E. (Geol. Survey), by C. F. Strangways, C. Reid, 

 and G. Barrow. 



