186 Reports and Proceedings— 
into seven horizons, characterized by their distinctive Ammonites, 
viz. Amm. communis, variabilis, striatulus, dispansus, the genus 
Dumortieria, Amm. Moorei and opalinus, and taking the striatulus- 
‘beds as a fixed starting-point, the author demonstrated how the 
strata varied in regard to that horizon. The Cotteswold Sands, 
containing the variabilis- and part of the communis-horizons, were 
below the striatulus-beds; the Midford Sands, containing the 
dispansus-horizon, were above. Gramm. striatulum occupying a thin 
bed at the base; the Yeovil Sands, containing the Moorei- and 
Dumortieria-horizon, and were consequently still later deposits. 
Since the different sands were deposited not on a horizontal plane, 
in point of time, but, as it were, obliquely, the deposit of Cotteswold, 
Sands having ceased before that of Yeovil Sands commenced, it was 
incorrect to lump all the “Sands” from the Cotteswolds to the 
Dorset coast under the single local name “ Midford Sands,” thereby 
implying a contemporaneity which did not exist, while the use of 
the present restricted local names was defended. 
The Ammonites were apparently uninfluenced by changes in the 
character of the deposit, since the same species are found in Lime- 
stone in the Cotteswolds, in Sands at Midford, and in argillaceous 
Marl at Ilminster. The change from argillaceous to arenaceous or 
calcareous deposits has been looked upon as so distinct a feature, 
that it has been utilized as a great argument in favour of drawing 
the line between Lias and Oolite at that point ; but if this be done, 
the line is always drawn at different horizons in different districts. 
If lithology furnishes no reason for a dividing-line at this point, 
it was shown that neither did paleontology. It was also shown 
that the Ammonite family Hilderoceratide dominated the period 
from the Falcifer- to the Concavus-zones, and that with the close of 
the latter zone they died out with singular abruptness, and that, 
furthermore, there exists, both in England and upon the continent, 
a marked hiatus at the same point due to the absence of a zone or a 
number of zones. 
On account of these facts the proposal was put forward that d’Or- 
bigny’s term ‘‘'Toarcien” should be employed to designate the strata 
from the Falcifer-zone to the Concavus-zone inclusive, that this term 
should not be used in the sense of merely an extended ‘“ Upper 
Lias,”’ but to mark an entirely distinct transition-formation,—a defi- 
nite part of the Jurassic period,—separating the typical Lias from 
the mass of thoroughly Oolitic strata. 
2. “On some Nodular Felstones of the Lleyn Peninsula.” By 
Miss Catherine A. Raisin, B.Sc. Communicated by Prof. T. G. 
Bonney, D.Se., LL.D., F.R.S., F.G.S. 
This paper dealt with two small masses of rock forming the head- 
lands of Pen-y-chain and Careg-y-defaid, a few miles from Pwellheli. 
They consist of old lava-flows, once glassy, now devitrified and, at 
the former place, associated with interbedded agglomeratic and ashy 
strata. The lithological characters, as well as other slight evidence 
obtained, would fully support the identification by the Survey of 
the surrounding beds as of Bala age. 
