MIDDLE LIAS: BATH. 211 
FT. IN. 
[Midford Sands.] Inferior Oolite, sands - - - 20 
iGrey clay - - - - - 2 
Upper Lias stone with Ammonites bifrons 
(Walcotti), A. serpentinus, &c. - 1 
Blue clay 30 
Brownish marlstone with A, capricornus 
(maculatus), Unicardium cardioides, Lingula 
Beani [?] abundant, Crustacea and 
Saurian teeth - - - 1 
TM-JJI T- -\ f Blue micaceous marl with nodules of iron- 
[Middle Lias.] j stone _ . 20 
The occurrence of A. capricornus in the "brownish marlstone/' 
together with the Lingula, is remarkable. Nevertheless much of 
the so-called " Marlstone " which is of an iron-shot character in 
the Kadstock area, occupies a different horizon from the Rock-bed 
at llminster ; and fossils of distinct stages are found sometimes 
together in a remanie condition. It seems reasonable to conclude 
that this " marlstone " of Dundas is likewise a remanie bed ; and 
that it occurs at the base of the Upper Lias. 
In the neighbourhood of Bath there are few sections in the 
strata between the Lower Lias limestones (Blue Lias) and the 
Midford Sands. Londsdale describes the beds filling this interval, 
as consisting of " Blue clay and marl ; which are tough in the 
lower part of the deposit, but thinly laminated and micaceous 
in the upper. Irregular beds of stone are interstratified with 
them." He estimates the thickness at 200 feet, and an old boring 
at Batheaston proved a thickness there of 170 feet. (See p. 135.) 
Along the Midland Railway between Bath and Combe Down, 
blue micaceous clay was exposed in several cuttings. It contains 
occasional bands of earthy limestone, but does not appear to be 
fossiliferous. It is capped by a bed of nodular iron-shot limestone 
that may represent the Marlstone, while above are three beds of 
limestone, the highest of which has yielded Upper Lias fossils. 
These hard bands in the Upper Lias sometimes resemble the 
Rock-bed of the Marlstone, and were evidently included with it 
by Lonsdale, in his section (at Box) of the strata overlying the 
blue clay and marl before mentioned. Indeed he remarks that 
" Interposed between the lias and inferior oolite are several beds 
of sandy marl, to which Mr. Smith gave the name of marlstone. 
They effect a gradual passage from the lias into the inferior 
oolite."* The fact is the Upper Lias is very thin in places, and 
we have little more than the basement-beds, overlaid by clays of 
no great thickness, that merge upwards into the Midford Sands. 
Thus, on the Geological Survey map near Bath, where the 
original survey and grouping of the divisions were undertaken 
primarily under Lonsdale's guidance, the Upper Lias has in some 
places been included with the Middle Lias, and in other places 
both these divisions have been included in the Lower Lias ; partly 
no doubt on account of the steep slopes, and the little space (on 
the one-inch map) to show the divisions ; and partly because rock- 
* Trans. Geol. Soc., ser. 2, vol. iii. pp. 243, 247. 
O 2 
