THE LAURENTIAN AND HURONIAN PERIODS. 7I 
the chambers are simply filled with crystalline carbonate of 
lime. When the originally porous fossil has been permeated 
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A 4 fo Peg 
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Fiz. 24.—Portion of one of the calcareous layers of Hozod, magnified roo diameters. 
a a, The proper wall (“‘ Nummuline layer”) of one of the chambers, showing the fine ver- 
tical tubuli with which it is penetrated, and which are slightly bent along the line @’ a’. 
cc, The intermediate skeleton, with numerous branched canals. The oblique lines are 
the cleavage planes of the carbonate of lime, extending across both the intermediate 
skeleton and the proper wall. (After Carpenter.) 
by a silicate, it is possible to dissolve away the whole of the 
calcareous skeleton by means of acids, leaving an accurate and 
beautiful cast of the chambers and the tubes connected with 
them in the insoluble silicate. 
The above are the actual appearances presented by Lozoon 
when examined microscopically, and it remains to see how 
far they enable us to decide upon its true position in the 
animal kingdom. Those who wish to study this interesting 
subject in detail must consult the admirable memoirs by Dr 
W. B. Carpenter and Principal Dawson: it will be enough 
here to indicate the results which have been arrived at. The 
only. animals at the present day which possess a continuous 
calcareous skeleton, perforated by pores and penetrated by 
canals, are certain organisms belonging to the group of the 
Foraminifera. We have had occasion before to speak of these 
animals, and as they are not conspicuous or commonly-known 
forms of life, it may be well to say a few words as to the 
structure of the living representatives of the group. The 
Foraminifera are all inhabitants of the sea, and are mostly of 
small or even microscopic dimensions. . Their bodies are com- 
