236 Reports & Proceedings—Geological Society of London. — 
3. March 22, 1916.—Dr. Alfred Harker, F.R.S., President, 
in the Chair. 
Dr. A. Smith Woodward, F.R.S., V.P.G.8., exhibited specimens 
of the problematical ichthyolite, Celorhynchus, trom an Eocene deposit 
in the Ombialla district, Southern Nigeria, and discussed the nature 
of this fossil. Microscope sections of the well-preserved Nigerian 
specimens confirmed W. C. Williamson’s determination that Celo- 
rhynchus is an essentially dermal structure. A similar section of 
part of the rostrum of the teleostean fish Blochius, from the Upper 
Kocene of Monte Bolea, near Verona, showed an almost identical 
structure. The precise nature of this rostrum remained to be deter- 
mined, but there could be no doubt that the so-called Celorhynehus 
is the corresponding part either of Blochius or of an allied genus. 
The following communication was read :-— 
‘‘The Pseudo-Tachylyte of Parijs (Orange Free State) and its 
Relation to ‘ Trap-Shotten Gneiss’ and ‘Flinty Crush-Rock’.” By 
S. James Shand, D.Sc., F.G.S., Professor of Geology in the Victoria 
College, Stellenbosch (S.A.). 
The rocks which are here described as ‘ pseudo-tachylyte’ occur in 
irregular veins in the granite-gneiss of Parijs (O.F.S.) ; they formed 
the subject of a communication to the Society on November 18, 1914, 
which has since been withdrawn. The author first regarded them 
as igneous intrusions ; in the account now presented he compares and 
contrasts these rocks with the ‘ trap-shotten gneiss’ of India and with 
‘flinty crush-rocks’ from Scotland, Argentina, and Namaqualand. 
The veins are utterly irregular in form, dip, and strike; they freel 
branch and anastomose, but not uncommonly terminate blindly. The 
material consists of a very dense black base, holding numerous 
rounded and subangular fragments of granite; these are sometimes 
so numerous that the base is reduced to the role of a mere cement 
between the rounded boulders. With regard to their microscopic 
characters, the rocks fall into three types, one of which is very 
opaque and almost without individualized grains or crystals, while 
the others represent different stages of crystallization of the first 
type. It is shown that the production of the veins involved 
a temperature sufficient to melt the felspar of the granite, and that 
there has been extensive recrystallization of felspar in the form of 
spherulites and microlites, and also of prisms of hornblende. In this 
evidence of very high temperature, and in the entire absence of 
shearing phenomena in the granite, the pseudo-tachylyte of Parijs 
ditfers from all known crush-rocks and has affinities rather with 
pitchstones and tachylytes. Among the crush-rocks of Scotland, 
however, the author (following Clough, Maufe, and Bailey) recognizes 
a passage from the clearly mylonitic type to a type in which fusion 
has been practically realized; the latter material is closely similar to 
the first of the Parijs types. A chemical analysis of the psendo- 
tachylyte shows that the total composition is practically that of 
a granodiorite, and is such as might correspond to an average of the 
very variable dark gneiss in which the veins occur. 
It is suggested that a ‘melt’ of granite, produced by mechanically 
developed heat arising from the sudden rupture of the granite, would 
