137 
The actual number of species common to the respective beds 
can as yet be estimated approximately only. It is true that much 
material is on hand, the ranks of collectors having been strongly 
reinforced of late years, but as the critical examination of the 
Pleurotomidae, Trochidae, and some other families is but little 
advanced, the published lists are necessarily defective. Additional 
identifications are frequently made, but pending an opportunity 
for publishing they may remain in manuscript for a long time. 
The observations made in this and former papers are based upon 
the published lists as revised to date by our manuscript additions 
and corrections. We should be glad if these latter could be 
printed herewith, but there is a limit, not only to the time at our 
disposal, but also to the space allowed us in the Society’s Trans- 
actions, and it must suffice to say at present that we shall take 
the earliest opportunity of furnishing revised tables of fossils. 
By far the most prolific Eocene deposit in Australia is that at 
Muddy Creek with 649 species of mollusca, and, as might be ex- 
pected, representatives of many of them are found in all the beds. 
At Spring Creek, out of a total of 320 molluscan species on our 
lists, 127, or 40 per cent., occur also at Muddy Creek. In their 
latest paper*, Messrs. Hall and Pritchard credit us with ad- 
mitting that there are two zones on the Spring Creek cliffs, but, 
as a fact, we purposely abstained from expressing a decided 
opinion on the matter until fuller investigations had been made. 
Our remarks are too long for quotation, but their meaning is clear 
enough from the concluding words, which are as follows :—‘‘ We 
offer the swgyestion that at this level, and above the echinoderm 
rock, a minor zone of the Eocene may possibly be demonstrated— 
at any rate the matter is worthy of further research.” Our doubts 
as to the existence of two zones at Spring Creek are increased 
rather than diminished by the list of fossils quoted by these 
authors from the upper clays. 
Amongst the 105 species enumerated from the clays, 40, or 38 
per cent., are represented at Muddy Creek, and for the sake of 
comparison we will make a similar calculation for the species of 
the so-called lower beds. Seven species are recorded by us as 
confined to the strata overlying the echinoderm rocky, and de- 
ducting these from our total of 320 species for the general sec- 
tion, 313 are left as proper to the inferior strata, of which 124 
are Muddy Creek species, giving a proportion of 40 per cent., 
which indicates a higher proportion of Muddy Creek shells 
in the lower than in the upper zone. And yet we are 
asked to believe that of these two zones it is the upper one 
which is more nearly allied to the HERS Creek bed! We 
r inane on the peswonea subdivision of the hacone fei ei 
Victoria. Proc. Roy. Soc., Vic., 1896. 
+ Correlation, é&c., Pt. IL. sp. 119: 
