140 Reports and Proceedings— 
Permian strata, mentioned in the title of his paper. The teeth 
described by Agassiz under the name of Diplodus have been already 
shown by Sir Philip Egerton to be associated with spines of the 
Pleuracanthus-type; and this identification was accepted by the 
author, who also showed that Xenacanthus, Beyrich, is identical with 
Pleuracanthus, and that, on the ground of priority, which there is 
no reason for disregarding, the latter name ought to be retained. 
_ With regard to Orthacanthus he indicated that in the type described 
by Agassiz the two rows of denticles are placed close together along 
the posterior face of the spine; while in his Plewracanthus the 
denticles are situated as far as possible apart on the sides of the 
spine. In the new Carboniferous species described in the present 
paper, and in those described and figured by the officers of the 
United-States Survey, the denticles occupy almost every intermediate 
position between these two extremes, and hence the author was 
inclined to unite Orthacanthus with Pleuracanthus. Compsacanthus, 
Newb., is also probably nearly related to Pleuracanthus. The author 
described in some detail the characters of the genus Pleuracanthus, 
and discussed its scientific position, with regard to which he inclined 
to the adoption of Dr. Rudolph Kner’s opinion that the Pleuracanths 
constitute a type of fish intermediate between the Hlasmobranch and 
Teleostean fishes, but more nearly approaching the latter, probably 
through the Siluroids. 
Ten species of the genus Plewracanthus, modified as above, were 
described by the author from the Coal-measures, principally of 
Yorkshire. Hight of these were described as new. 
2. “On the Schistose Volcanic Rocks occurring on the West of 
Dartmoor, with some Notes on the Structure of the Brent-Tor Vol- 
cano.” By Frank Rutley, Esq., F.G.S. 
Among the ashy beds of this district are certain amygdaloidal 
schistose rocks, which the author is of opinion are really lava-flows, 
which have probably been crushed or infiltrated, and have so as- 
sumed a foliated structure owing to pressure from superincumbent 
beds acting on rocks thus constituted. They are much altered, but 
were probably once basalts. The anthor considered it very probable 
that these schistose beds and Brent Tor, considered to be of Carbon- 
iferous age, are identical with beds near Tavistock and in the Saltash 
district, which are of Upper Devonian age. 
In the concluding part of the paper the author described the beds 
of alternating ashes and lava, now much disturbed by faults, which 
constitute all that remains of the ancient Brent-Tor Volcano, and 
endeavoured, from the evidence which can be thus obtained, to give 
a probable reconstruction of the former cone. 
3. “On Mammalian Remains and Tree-trunks in Quaternary 
Sands at Reading.” By EH. B. Poulton, Esq., F.G.S. 
. The author described in detail a pit opened on the south slope of 
the Thames Valley on the Redland Hstate at Reading, about 36 feet 
above the river-level. The north face shows gravels and alluvia con- 
taining chalk-flints and fossils, fragments of Oolitic limestone and 
fossils, and scattered materials of the high-level gravels overlying 
