MIDDLE LIAS: FREES. 243 
In the northern part of Lincolnshire the succession of beds, 
grouped as Middle Lias by Mr. Ussher, is as follows : * 
Rock Bed. 
Clay, with lines of nodules and septaria 6 feet. 
Pecten-bed ironstone. 
The fauna of the Pecten-bed, and of part at any rate of the 
overlying clay, is rather that of the higher portions of the Lower 
Lias elsewhere, than that of the beds with Ammonites margaritatus 
exposed south of Lincoln. At present no specimens of Ammonites 
m.arqaritatns have been found in the clay below the Rock Bed, 
while A. capricornus has been found in nodules that occur within 
a few feet of it. Hence on palaeontological grounds there is a 
remarkable attenuation of the zone of A. margaritatus. 
The Rock-bed is a grey and brown ferruginous limestone or 
ironstone, 7 to 10 feet thick. From the abundance of 
Rhynchonella tetrahedra it was named the Rhynchonella-bed by the 
Rev. J. E. Cross. It has been traced through Grayingham and 
Kirton Lindsey, and has been quarried in places between 
Kirton and Manton. The rock is here and there nodular, but 
nowhere rich enough in iron to be of value for smelting. Some 
fossils were obtained by Mr. Cross in the railway-cutting south of 
Santon Warren : these include Ammonites spinatus, A. communis, 
Belemnites paxillosus, Terebratula punctata, &c.f 
Northwards the Rock-bed has not been well exposed, except at 
Winteringham, where it was observed by Mr. C. Fox-Strangways. 
Beyond this village it disappears beneath the Alluvium of the 
Humber. 
Shropshire. 
The occurrence of Middle Lias, at Frees in Shropshire, was 
made known by Murchison in 1834. He remarked that the 
Marlstone was to be seen " in quarries and by the sides of the 
roads, dipping to the north-north-east at low angles ; " and he 
recorded a number of fossils which clearly established the age of 
the strata. J 
During my examination of the district I was much indebted to 
Mr. Henry Ikin of Frees, who pointed out the spots where 
exposures of the beds were to be seen ; and who had collected a 
series of fossils which he submitted to Messrs. Sharman and 
Newton for identification. 
It will be seen that not only the Lower Lias, wherever evidence 
was to be obtained, but also the Middle Lias, presents the same 
general characters as are met with along the main outcrop of the 
strata in the midland counties. 
The fossiliferous beds of sandy Marlstone have been opened up 
in graves in the churchyard at Frees, and from these beds Mr. Ikin 
has obtained many of the fossils mentioned. Here the thickness 
of the stone-beds is from 8 to 10 feet, including at the base, 
* Geol. Lincoln, pp. 31, 32. 
| Quart. Journ. Geol. Soc., vol. xxxi. p. 124. 
J Proc. Geol. Soc. vol. ii., p. 115 ; and Silurian System, p. 23. 
Q 2 
