64 
THE LIAS MARLSTONE OF LEICESTERSHIRE. 
fossils, though they belong as a rule to a very limited number 
of species. These beds, termed “ Jacks” by the quarrymen, 
are made up of an agglomeration of the shells of Rhynchonella 
tetraedra and Tercbratuia punctata, associated with which 
we also find Belemnites paxillosus and Belemnites elongatus. 
The hitter forms serve to distinguish the Lias marlstone from 
the Northampton Sands ironstone, to which it bears a con¬ 
siderable lithological resemblance, but from which it is both 
geologically and mineralogically quite distinct. Certain beds 
are almost entirely composed of encrinite fragments or of 
broken shells. Now and then an Ammonites spinatus will 
turn up, but this, the characteristic fossil of the Marlstone 
horizon, is in the Leicestershire district generally characteristic 
by its rarity or entire absence. The bottom bed of the Marl¬ 
stone usually contains small fiattish phosphatic nodules in 
such numbers as to give the rock a conglomeratic aspect. 
Having described the general features of the Marlstone 
Bock, as exhibited in the counties of Leicester, Rutland, and 
(South) Lincoln, I will now proceed to notice in somewhat 
greater detail its varying character and thickness, and in 
particular its mineral products and organic remains within 
the limits of the above district. For convenience we will 
commence in the centre of Rutland, a typical Marlstone 
country, and thence trace the rock southwards towards 
Northamptonshire, and northwards into Lincolnshire. 
In the neighbourhood of Oakham the Rock-bed, though 
only eight or nine feet in thickness, covers a very extensive 
area of low-lying ground forming the fioor of the famous 
Yale of Catmos. Its decomposition gives rise to the highly 
productive red soil for which this district is renowned, and 
which probably gave the name Rutland (Red-land) to the 
county. A little further to the south this rock may be seen 
forming terraces on the sides of the valleys of the Cliater 
and Gwasli. To the north of Oakham, about Teigh, Edmond- 
tliorpe, and Wymondham, the Marlstone Rock stands out as a 
bold escarpment on the west, with a gentle dip-slope to the 
east. Going westwards from here we find the Rock-bed 
stretching out by Whissendine and Pickwell to terminate in 
the bold promontory of Burrow-on-the-Hill. This district, 
diversified as it is by deep valleys and surmounted by the 
cliff-like masses of the Rock-bed, displays hereabouts 
really picturesque scenery. Bending round by Somerby and 
Ouston the Marlstone sends out another fine branch by 
Tilton to Billesdon. This western projection of the Marlstone 
is due to the preservative influence of the great Billesdon 
and Lodington fault, which has a downthrow to the north of 
