62 
The Australasian Scientific Magazine . [Sept, i, 1885. 
into combination with the calcium it must expel the carbon. Now when 
we poured the acid on the limestone, the effervesence you observed was in 
reality a chemical change taking place, the atoms of chlorine were com- 
bining with the atoms of calcium to form chloride of calcium (or chloride 
of lime), that white powder which you see is left on the stone, while the 
carbon so unceremoniously expelled is, by the laws of chemical affinity, 
combining with the oxygen gas of the air to form carbonic acid gas, which 
produces such a disagreeable smell. By this simple test you may always tell 
whether the rock you are examining is a limestone, or contains lime in any 
quantity. You have now noted with the compass the direction of the 
strike, or the line made by the stratum with the horizon, and showing the 
direction of the stratum across the country, which you found to be N.W. 
You have also noted the dip, or inclination of the beds, with the clino- 
meter, which is here found to be 6o° to the S.W., for, as you will see by- 
and-bye, the dip is always at right angles to the line of strike. The beds 
are not of equal thickness, nor yet of equal hardness, some of the bands 
are no thicker than a piece of cardboard, others are quite four feet thick, 
some are dark blue and sub crystalline, others are soft and earthy, but 
stay ! what is this marking on that piece you have just broken off with the 
hammer? Ah ! you have made a discovery; it is a fossil, and an interesting 
one, it is of a characteristic marine organism, or rather the covering of one. 
A fossil mollusc which will enable us to ascertain the relative age of these 
limestone rocks and the conditions under which they were formed. That 
fossil is Sperifora laevicosta. A mollusc of the class Palliobranchiata, 
order Brachipoda, of Middle Devonian age. And here, in this yellowish 
lower sand, I have discovered another fossil of different shape, it is a 
Pterinia, also a mollusc, but what is that you have in the piece of whitish 
rock you have just broken ? Ah that is Atrypa reticularis but this species is 
not confined to this formation, it is found in the older and underlying 
palsegoic rocks, the upper silurian, but it is here much larger than 
it is found elsewhere in the silurian sedimentary rocks. Again this short 
club-like piece of rock with circular rings or markings, what is this? Surely 
this is not a member of the nautilis family. Yes, it is indeed, for if we 
turn to page eighteen of “ Prodomus of the Palaeontology of Victoria/’ 
we will find it named as Phragmoteras Subtrigonum, of the class Cephalo- 
poda, order Tentaculifera, hitherto known only from the Buchan lime- 
stones, some fifty miles distant. To our learned government Palaeontolo- 
gist, Professor M c Coy, we are indebted for drawings and descriptions of 
various molluscs hitherto found in Victoria which have enabled us to 
identify these species. 
(To be continued ). 
