200 J. W. Dawson—NMobius on Hozoon Canadense. 
objection, not original with him, is derived from their unequal 
dimensions. It is true that they are very unequal in size, but 
there is some definiteness about this. They are larger in the 
thicker and earlier formed layers, smaller or even wanting in 
the thinner and more superficial. In some slices the thicker 
trunks only are preserved, the slender branches having been 
filled with dolomite or calcite. It is difficult, also, to obtain, 
Cenostroma and Caunopora. In illustration of this I give in 
fig. 5 a group of these canals from a recent paper of my 
own. 
4. A fatal defect in the mode of treatment pursued by 
Mobius is that he regards each of the structures separately, 
and does not sufficiently consider their cumulative force when 
taken together. In this aspect, the case of Hozoo be pre: 
sented thus: (1.) It occurs in certain layers of widely dis- 
tributed limestones, evidently of aqueous origin, and on other 
grounds presumably organic. (2.) Its general form, lamina 
tion and chambers, resemble those of the Silurian Stromatopora 
and its allies, and of such modern sessile foraminifera as Carpen- 
teria and Polytrema. (8.) It shows under the microscope 4 
tubulated proper wall similar to that of the Nummulites, 
though of even finer texture. (4.) It shows also in the thicker 
layers a secondary or supplemental skeleton with canals. (5) 
These forms appear more or less perfectly in specimens miner- 
in a very early Protozoan. (7.) It has been found in various 
arts of the world under very similar forms, and in beds 
approximately of the same geological horizon. (8.) It may be 
*I have succeeded best in this by etching the surface of broken specimens. 
+ Journal of London Geological Society, January, 1878. 
