3 
a great extent of country and accumulated during more than thirty years 
work, at a cost of untold fatigue, of great danger and sacrifices of all kinds, 
such as only an ardent love of science in him to whom these treasures belong 
— the Eev. W. B. Clarke — has been able to render endurable with courage 
and patience. 
In paying homage to his devotion I fulfil a debt of gratitude that 
assuredly all who have at heart the progress of Geology and Palaeontology 
will appreciate. 
Mr. Clarke in submitting to me the Palaeozoic Possils collected through 
his diligence in New South Wales, has wished to verify his own observations 
and establish undeniably their correctness by a means he has no fear of 
employing even at a distance of live thousand leagues from the country 
explored by him, at the time when by an inconceivable distortion of meaning, 
some geologists have disdained to make use of them, although having them 
at their hand, to arrive more surely and quickly at a methodical classification 
of the formations, the elucidation of which had been entrusted to them. 
So as to attain his object more surely, Mr. Clarke has taken care to 
influence me in no way, and to furnish me with no information beyond that 
which concerns the locality of the occurrence of each specimen. 
He has thus left me quite free to form my opinions, and I have had as a 
sole clue to this labyrinth of the varying forms submitted to my examination 
the ideas acquired at the cost of a long experience and thorough and 
conscientious studies to enable me to group them and refer them to each of 
the main Palaeozoic Systems to which they belong. 
This experience was all the more necessary in the present case, when 
the greater portion of the species are preserved only as impressions or casts, 
and without it I should have found myself in the most hopeless confusion. 
In making these observations I am far from pretending that all my 
specific determinations are quite correct and free from error ; in this respect I 
am the first to admit that I have many doubts on account of the imperfect 
state of the specimens examined by me. Nothing, however, is opposed to 
to the fact that, by the exact knowledge of the relations of shape and 
organization, one is able to recognise definitely the horizon of each of these 
specimens. 
c 
