NOTICE.

(TO PRECEDE THE FOURTH EDITION OF ' SILURIA.')
 

The reader of this edition will find that a very important change has been
made in my views as given in former editions, respecting the age of the
Upper Sandstones of Elgin and Ross-shire, which I have hitherto classed
with the Devonian or Old Red Sandstone. My previous conclusion was
founded entirely on the strong natural evidence presented, to me, by the
conformable superposition of those beds to the strata of the inferior and
unequivocal Old Red Sandstone replete with its well-known fossils. This
opinion was confirmed by the examination of the rocks in question by
Professor Ramsay, Professor Harkness, the Rev. George Gordon, the Rev.
J. M. Joass and others.

The existence, in strata of Devonian age, of reptiles of so high a class as
the Telerpeton (see fig. 73 in my last edition, p. 289) and the Stagonolepis
was not, indeed, admitted by me without great reluctance, inasmuch
as, if eventually substantiated, it would have weakened the main argu¬
ment that runs through all my writings, which shows a regular pro¬
gression from lower to higher grades of animals, in ascending from the
older to the younger formations. Most joyfully, therefore, did I welcome
the remarkable identification by Professor Huxley of the Hyperodapedon
of the New Red Sandstone of Warwickshire with the Hyperodapedon of
Elgin ; and bowing, as I have always done, to clear palaeontological proof^
I have now excluded aU that portion of my former editions which placed
these reptiles in the Old Red Sandstone.

The importance of this rectification, due to my eminent associate, has
very recently received a wide extension; for among the fossil remains
collected in India by the late Rev. S. Hislop, Professor Huxley has also
found the Hyperodapedon.

The formation in India containing this reptile has been considered by
Professor Oldham, the Director of the Indian Geological Survey, to be
either the Trias (New Red Sandstone) or the representative of an intermede
between the Palaeozoic and Mesozoic rocks. In all probability this cor¬
relation will have to be extended to Soiith Africa, since one of the
characteristic fossil reptiles of that country, the Dicynodon, has been found
in the Ranigunj beds of this age in India.

I take this opportunity of further stating that I have not adverted in
the Preface to a great number of important additions which I have made in
this edition; they are, in fact, so numerous that, if a smaller type had not
been used, the work would have been swollen to an unreadable size.

RODERICK I. MURCHISON.
Oct. 30, 1867.