110 CALCISPHARA. 
Concerning the Sponges, PRor. SOLLAs writes—‘‘ The line 
between the calcareous Sponges and the silicious ones is well 
marked, and no one who knows anything about the Sponges 
would venture for a moment to doubt that Szphonia, Pharetro 
spongia, and Stauronema, are fossil Lithistids, Renicrids and 
Hexactinellids respectively, yet these divisions of the sponges 
are in a recent state never anything but silicious in composition, 
while in their fossil representatives they are sometimes silicious, 
but as often calcareous in composition.” 
The present notice I am aware by no means solves the 
problem as to what Calcisphere really are. My object has been 
to help on the discussion, and to give additional information as 
to their occurrence and distribution among the Carboniferous 
beds, and to shew that the difficulties in the way of their 
Radiolarian affinities are not so great as imagined by 
Pror. WILLIAMSON. 
My own impression is that among the species of Calcisphera 
which he has described, future research will show that there 
are included both Foraminifera and Radiolaria. 
In connection with Foraminifera, I may mention that at 
Minera, at a little higher horizon in the Mountain Limestone 
than the present, there are several bands of stone, amounting 
altogether to some twenty feet in thickness, in which Fora- 
minifera are specially abundant, and particularly Saccammina 
Carter’ (Brady), which in some of the layers has almost exclu- 
sive possession of the stone. The quarry in which the best 
exposures are to be seen, is at the back of the office of the 
Minera Lime Company. This Saccamminal Limestone, on 
analysis by my son, gave the following results :— 
Carbonate of Lime. AT 3 wa «aye 95526 
Carbonate of Magnesia ,. a ai Phe ee ee 
Insoluble Silicates Se ae yr ae 65 
Tron Oxide and Alumina a . ee AG 
Moisture 4c 55 Me ae fA sats 
Organic matter and Phosphoric Acid .. .. traces 
