VOL. XIV. (1) MENDIP ARCHIPELAGO. 65 
seems to have occurred about the close of the 
period, for the basement bed at Lassington is of remanie 
nature: this is the case also at Binton. Signs of 
erosion also occur at Curry Rivell, but are so slight that 
only a non-sequence results. A freplanorbis con- 
glomerate is exposed near Goblincombe Farm, above 
Wrington, where scales and teeth of fish are embedded 
in an argillaceous matrix, with angular limestone fragments 
included. 
At the commencement of Liassic times, the main 
physiographic features were similar to those of the pre- 
ceding period. The area of the islands, as shown by the 
Rhetic strata, had been reduced by the encroachment of 
that sea. Several of the smaller islands, and probably 
Wrington, were submerged before the deposition of the 
Psiloceras planorbis strata. Subsidence of the Mendip 
archipelago appears to have been only slight in the 
Liassic epoch, and there were frequent slight elevations 
of certain areas," and reconstruction of some of the 
layers. In the Radstock district there is evidence of six 
ammonite zones in about ten feet.7, The Mendip Lower 
Lias marginal deposits may be first considered. 
Near Downside, Shepton Mallet, are strata derived 
chiefly from the Carboniferous Limestone, in which no 
marked divisions occur. These are exposed in the road- 
cutting leading from Shepton Mallet Church towards 
Downside, and south of the Midland Railway; and also 
in a quarry near the viaduct.2 In the quarry is an im- 
persistent bed of conglomerate, composed chiefly of 
pebbles of chert and Carboniferous Limestone; with a 
few quartz pebbles, perhaps derived from the Old Red 
Sandstone of Downhead Common. The Downside beds 
I Quart. Journ. Geol. Soc., vol. lvii., p. 154. 
2 H. B. Woodward, “ Geology of England and Wales,” (1887), p. 266. 
3 Mem. Geol. Surv., “ Jurassic Rocks, etc.,” (1893), vol. iii., p. 88. 
