TRANSACTIONS OF SECTION C. 517 
effects of weathering and decomposition than the marlstone itself, which occurs 
some 3 feet or 4 feet lower in the section. This is to be found also on Tilton 
Hill, indicating there also the existence of higher beds than previously known. 
Its composition was much like some forest marbles, entirely differing from that 
of beds above or below, though traces of a similar structure occurred less 
regularly, but neyer as a definite layer or seam, in other parts of the section. 
The horizon of Wilson’s type specimen of Eodiadema granulata had never been 
definitely ascertained, nor indeed that of the majority of the gasteropods, &c., 
described by him as coming from Tilton, but found in the débris used in the con- 
struction of the East Norton embankment. 
The Billesdon Coplow section solved this question, for there the same echinoderm 
was found with a number of the same genera and species of gasteropoda, cephalo- 
poda, &c. It had also been found by others, and there was an example from 
Desborough in the Invertebrate Department of the Leicester Museum under the 
writer’s charge. 
In conclusion the author wished to reiterate his remarks as to the importance 
for zonal purposes of this gasteropod band of the Transition bed of the middle 
lias. : 
The character of the fauna stamped it decidedly as purely littoral or coastal, 
whilst that of the beds below, containing as they did chiefly brachiopoda and 
deeper-water lamellibranchs and cephalopods, pointed to their being of a more 
pelagic nature, 
It marked a change in the physical conditions which predominated at that 
period, and as such was rightly named a ‘Transition bed, for the Upper Lias 
fauna was itself only a modification of it, with some ditferences of lithological 
composition in the strata and of species in the fauna which characterised it. 
Probably the inset of more littoral conditions took place between the formation 
of the thick encrinital seam mentioned above and that of the Transition bed. 
Certainly pelagic conditions, judging from the lithology and fauna of the beds 
below, seemed to come to a close about the time when this encrinital seam was 
deposited. 
The thickness of the strata and the fauna of the two sections, the one at Tilton as 
described by Wilson and the other as discovered at Billesdon Coplow by the writer, 
were, with some slight differences, due to local causes, more or less identical. 
7. On the Occurrence of Boulders of Strontia in the Upper Triassic Marls 
_ of Abbots Leigh, near Bristol. By Hersert Bouron, F.R.S.£., 
F.G.S., and C. J. WATERFALL. 
A considerable area of the park attached to Leigh Court, near Bristol, has 
been found to be underlaid by a remarkable deposit of huge boulders of strontia 
embedded in Triassic marls. The boulders in various places appear above the 
surface. The soil varies in depth from a few inches to 4 feet, and rests upon the 
irregular surface of the marl-beds containing strontia. The boulders of strontia 
are found of all sizes, from a pea up to masses estimated at 100 tons in weight. 
In one instance the breaking-up of a single boulder of strontia occupied six men 
for five weeks. Six hundred of tons of the mineral were found in one pit 15 yards 
long by 21 yards wide. 
The upper surface of the boulders is usually deeply grooved, the grooves 
running approximately north and south. The boulders readily split into slabs 
along lines coinciding with the grooves. The deposit up to the present has not 
exceeded a greater depth than 11 feet, The yield of strontia is about 2,000 tons 
per acre. 
8. Notes on the Ancient Volcanoes of Basutoland. By Rev. 8. 8. Dornan. 
Basutvland is a high plateau between the Vaal and the Orange Rivers. It is 
the culminating point of the great plateau which fills the whole interior of the 
