242 LIAS Or ENGLAND AND WALES: 
Excepting in Yorkshire and (I may add) in Raasay, we have 
elsewhere no record of the occurrence of A. capricornus and 
A. margaritatus in the same stratum, but inasmuch as there is 
no recognizable plane of demarcation between the zones of these 
Ammonites, indicating any cessation in the continuity of deposit, 
it would not be very surprising to find the two species together, 
for the associated fossils indicate a blending of the zones. Indeed, 
in the list given by Mr. Ussher from the clays beneath the nodule 
bed, it has not been practicable to separate the species from the 
two zones. 
From the nodule-bed the following species were obtained* : 
X Ammonites margaritatus. 
Belemnites vulgaris. 
X Amberleya imbricata. 
Turbo. 
Avicula cygnipes. 
X Gresslya donaciformis. 
X Pleuromya costata. 
Plicatula spinosa. 
X Unicardium cardioides. 
xWaldheimia perforata. 
Ceromya petricosa (liassica). 
The species thus marked X were obtained also from the clays below. 
The higher beds of the Middle Lias, that have been exposed 
at Kirk and Parry's pit to the north-east of Bracebridge, 
consist of shales with ferruginous septaria ; and about 6 feet above 
the " Nodule-bed " there was to be seen a band, described by Mr. 
Ussher as ''Ferruginous rubble, suggesting a thin weathered 
representative of the Marlstone Rock-bed." This suggestion 
may account for the non-appearance of the rock-bed in places, as 
near Yeovil, where this thin layer is often so decomposed as to 
make no feature at the surface. 
Among the fossils from this pit, above and below the Module- 
bed, may be noted Ammonites nitescens, Lcda graphica, L. 
imbricata, Avicula cygnipes, A. incequivalvis, Area Strickland!, 
Cardinm truncatum, Hippopodium, Inoceramus, Ostrea irregularis, 
and Pecten lunularis^ as well as some of the species noted from 
the nodule-bed at Bracebridge. 
The Nodule-bed has been traced by the race-course, north-west 
of Lincoln, where it consists of ironstone with phosphatic pebbles. 
Of the lower beds, we rarely find exposures along the fi/ot of the 
escarpment, north of Lincoln, but a few fossils have been obtained 
from a brickyard south-west of Hemswell. 
Between Willoughton and Willoughton Grange, traces of an 
ironstone-bed were observed by Mr. Ussher, and these he takes 
to be indications of the Pecten-bed, which is an important horizon 
further north. 
The Marlstone Rock-bed sets in north of Burton-by-Lincoln, 
and its narrow outcrop forms a foundation for a number of vil- 
lages. There are however few exposures, and these furnish 
evidence of but 3 or 4 feet of hard ferruginous sandy limestone, 
sometimes crowded with fossils. Ammonites communis, Belemnites 
Ireviformis, Cardinia crassitiscula, Pecten aquivalvis, P. lumdaris, 
Waldheimia perforata, Terebratula punctata, and other fossils 
have been obtained at South Carlton, Ingham, and Fillingham. 
* Geol. Lincoln, p. 28. 
