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THE POPULAR SCIENCE MONTHLY. 



dawn-animal. Logan speaks of it in his first remarks upon them, 

 referring more particularly to their weathered outcrops and somewhat 

 concentric structure ; while Dawson sees much in their internal organi- 

 zation suggestive of a fitness for foraminiferal requirement. The 

 layer seems better arranged for sheltering a gelatinous body, throwing 

 out pseudopodia reaching after food, than for accommodating the 



1 



Fig. 9. Stromatopoea Concentbica. (Goldf.) 



1. Surface of a small hemispheric mass, showing the edges of the thin laminae unequally weathered, 



natural size. 



2. Magnified portion, showing weathered edges of successive lamina?, which are indented by pores. 



3. More highly-magnified portion of the specimen, showing the walls and tubulation. 



sponge animals, subsisting through the passage of currents of water. 

 The canal system, with the supplemental skeleton, is wanting in this 

 genus, but appears in the allied forms of the Devonian. 



A very important feature of the greenstone fossils is their mineral 

 composition. They are composed of silicates, very probably of feld- 

 spar. Mr. Hawes has not been able yet to satisfy himself fully as to 

 the nature of the silicate, because of the smallness of the particles 

 obtained. A drop of acid placed upon one of the specimens exhibited 

 a slight effervescence, indicating the traces of carbonate of lime 

 perhaps part of the original foraminifer before its fracture and disper- 

 sion in the mud. He suggests that the presence of these lime-struct- 

 ures afforded the material for the manufacture of so much labradorite 

 in the diabases containing the fossils. 



