CARBONIFEROUS VOLCANIC ROCKS OF SOMERSET 195 
divided by partings of fine tuff. A more prolonged and 
vigorous discharge of ashes is indicated by a band of green 
tuffs about 9 feet thick (11). The base of this band passes 
down into the ashy limestone group (10) below, so that there 
was obviously no interruption in the continuity of the 
volcanic phenomena. But the discharge of the ashes must 
have been sufficiently gentle or intermittent to allow of 
the continued presence of living organisms even on the 
bottom over which the volcanic detritus was accumulating, 
for the tuff contains lenticular seams and nodules of crinoi- 
dal limestone. In this band one of the characteristic 
features of Carboniferous tuffs already referred to is well 
displayed — the presence of abundant lapilli of a minutely 
vesicular basic pumice. A thin slice prepared from one of 
the calcareous bands was found under the microscope to 
be full of these lapilli and of various organisms, among 
which Mr. Newton detected foraminifera (Endothyra ?), 
and probably also echinoderms, corals, and entomostraca. 
“ The gradual cessation of volcanic activity was marked 
by a return of the phase of sedimentation that had preceded 
the last more violent outbreak. The tuff-band just de- 
scribed passes upward into a' red limestone (12) about three 
feet thick, banded with lenticular seams of green tuff like 
that underneath. Then comes a reddish nodular limestone 
(13), about three feet thick, with irregular partings of a 
ferruginous argillaceous material which may be highly 
decomposed volcanic detritus of the finest kind, marking 
some of the last efforts of the expiring volcano. Immedi- 
ately above lies the ordinary well-bedded coarsely-crinoidal 
limestone of the district. Its lower seams include little 
blotches which may possibly also be decayed ashy material. 
But above this part of the section all trace of volcanic 
activity disappears, and the normal limestone, made up 
entirely of organic remains, resumes its place.” 
We have very little to add to the above description. 
