106 
Geological Summary. 
The elucidation of the fossils whose descriptions precede this has given 
me a great deal of trouble, and I have succeeded in determining them only 
after patient examination and numerous comparisons ivith European and 
American specimens, of the determination of which there is not the least donht. 
I cannot, however, he certain that, in spite of all my endeavours to arrive at a 
definite result, some errors may not have crept into the list of species I 
consider to be Devonian. Though this may have happened, I think I can 
assert, in all certainty, that the number of these ivill be so small that it can 
have no etfect on the conclusions that follow, and cannot modify them to the 
slightest extent. 
Of the eighty-one species observed, including a new sponge not 
described because of the impossibility of determining its genus, as well as a 
stem of Bhodocrimis, there are but five that can be considered, with certainty, 
as coming from Upper Devonian beds. 
These are : — 
Stroplialisia prodnetoides, Murchison. 
Chonetes coronata, Conrad. 
Rhynchonella pleurodon, Phillips. 
Sp)irife7^ disjimcius, Sowerby. 
Amculopccten Clarhei, L. G. de Koninck. 
All the others, or at any rate the greater number, and principally 
those that are found in the black limestone of the Yass District, belong to a 
geological horizon a little lower than that which has yielded the species I 
have just quoted, but still more recent than those that are so well charac- 
terised by the presence of Calceola sandalina, Lamarck, of which I. have not 
seen traces, any more than the Trilobites usually associated with it, Among 
these eighty-one species thirty are new to science, and are known only in 
Australia; but it must be noted that, Avith the exception of four of them, all 
have their analogues in Europe and America. These four species are : — 
ArchcEOcyathus ? Clarhei, L. G. de Koninck. 
BiUingsia alveolaris, ,, 
Niso ? Rarwinil, ,, 
3HtclieUia striatula, ,, 
