Geological Society of London. — 235 
many places. No active volcano now exists in the island, but the 
occasional emission of carbonic-acid gas, the occurrence of numerous 
hot springs and deposits of siliceous sinter, and the frequency of 
small earthquake-shocks, seem to show that volcanic forces are only 
dormant and not entirely extinct. 
The ashes generally lie most thickly on the side of the cone 
between north and west; this is accounted for by the prevalence 
of the south-east trade-winds. The volcanic areas are ranged 
roughly in a linear direction, corresponding with the longer axis 
of the island. 
Sedimentary rocks occur mainly on the western and southern 
sides of the island. The relations of these to each other have not 
yet been determined; but from the fossils (referred to the European 
standard) it seems that the following formations are represented :— 
Hocene, Upper Cretaceous, Neocomian, Oxfordian, Lower Oolites, 
Lias. Possibly some of the slaty beds may turn out to be Silurian 
or Cambrian. The crystalline schists, etc., are probably, for the 
most part at least, Archean. Recent deposits fringe the coasts and 
are largely developed on the southern part of the island. 
Hast of the central line of watershed there is a long depression 
containing a wide alluvial deposit, probably an old lake-bed. Ter- 
races fringe its sides in many places. The lagoons of the eastern 
coast are due to alluvial deposits. 
The paper concluded with some remarks on the geological an- 
tiquity of the island, its separation dating from early Pliocene times, 
if not earlier. This is the conclusion arrived at by Wallace from 
its fauna; the author’s detailed researches into its flora, recently 
described before the Linnean Society, show that while about five- 
sixths of its genera of plants are also found elsewhere, chiefly in 
tropical countries, at least four-fifths of its species are peculiar to 
Madagascar. 
The Appendix, drawn up by Mr. R. Bullen Newton, F.G.S., con- 
sisted of Notes upon the fossils collected by the author, with tables, 
and descriptions of two new species, namely, Astarte (?) Baroni and 
Sphera madagascariensis, both from deposits of Lower-Oolitic age. 
3. “Notes on the Petrographical Characters of some Rocks col- 
lected in Madagascar by the Rev. R. Baron.” By F. H. Hatch, 
Ph.D., F.G.S. 
This paper was divided into two parts, the first treating of the 
petrographical characters of the older crystalline rocks of the eastern 
and mountainous part of the island, the second of the nature of the 
lavas that have been erupted from volcanic vents situated mainly 
in the same portion of the island. 
i. The Older Crystalline Rocks are represented in Mr. Baron’s 
collection partly by foliated specimens, partly by rocks showing no 
parallel structure in the hand-specimen. 
The foliated specimens have, with few exceptions, the structure 
and composition of gneiss. The author subdivided them into an 
acid and a basic series. The acid series, which embraces rocks com- 
posed of abundant quartz with orthoclase as the dominant felspar, 
