194 CARBONIFEROUS VOLCANIC ROCKS OF SOMERSET 
fossils, about 3 feet thick, but swelling out to a much 
greater bulk further east. Next comes a group of green 
and red tuffs (4) with lenticular bands of limestone. Some 
of the tuffs are marked by bunches of coral in the position 
of growth. At the top of these tuffs a band of red ferru- 
ginous limestone (5) appears ; it is thin-bedded, lenticular, 
and about 5 feet thick. It passes upward into about 
15 feet of highly fossiliferous limestone (6). The quiet 
interval marked by the intercalation of this crowded mass 
of organic remains was brought to an end by a much more 
vigorous display of volcanic energy. The explosions 
began with the discharge of ashes, which in the section are 
now represented by from 12 to 14 feet of green tuff (7). 
The lapilli varied continually in size so that the tuff is made 
up of lenticular layers of fine and coarser material. The 
band, moreover, is much veined with calcite, no doubt 
derived from the solution of calcareous organisms either in 
the surrounding limestones or in the tuff itself. The top of 
this accumulation of pyroclastic material is marked by a 
thin red cherty layer (8), immediately above which lies the 
chief member of the volcanic group — a dull green amygda- 
loid of the usual basic character (9). This bed, perhaps 
12 to 14 feet in thickness, has been a thoroughly vesicular 
scoriaceous basalt. It shows the ‘ pillow ’ structure 
already referred to, some of the ‘ pillows ’ being a yard or 
more in diameter. The vesicles, sometimes 4 inches long, 
have been filled with calcite. The upper surface of the 
sheet is rugged and scoriform, and the overlying sediments 
have filled up its hollows. 
“ The outflow of this lava was followed by a much quieter 
phase of volcanic activity, when only occasional showers 
of dust were discharged over the floor of the sea on which 
the calcareous organisms had again spread. This portion 
of the record is contained in a band, about 9 feet thick, of 
lenticular seams of blue limestone (10), full of fossils, and 
