GALENA FORMATION CONGLOMERATE 271 



Manitoba.^ Where there is a predominance of shale, that material takes 

 the place of the less calcareous part of the rock, while the more calcare- 

 ous part lies in more or less abundance in layers, lenses, and nodular 

 patches within the shale. In the base of bed number 3 lumps, cakes, and 

 lenses of pure light-colored, fine-grained limestone lie isolated in a brown 

 fucoidal shale, and the evidence is there very clear that the lime was 

 originally deposited in lumps or masses. The lime quite certainly came 

 mainly from the decomposition of marine algae in the manner lately de- 

 scribed by Thomas C. Brown.^ Without entering into a discussion of the 

 question as to what plants and animals may have contributed to the lime 

 deposit, or in what manner the lime was collected, it is sufficiently evi- 

 dent to me that something deposited lime in small and large masses. 

 The lenses and lumpy patches of relatively pure lime in all parts of the 

 Galena-Trenton frequently inclose fossil shells, etcetera, in a way to 

 show that these lime bodies were soft when deposited — that is to say, 

 they often partly inclose shells, stipes of graptolites, fucoids, etcetera, 

 either in the manner of objects overflowed by soft lime or in the manner 

 of objects partly sunken into such a soft deposit. Shells of Lingula are 

 found which had bored into them, and the boring was, of course, done 

 while they were not yet consolidated. In case of the bed number 6, the 

 strata consist partly of clay-shale that was deposited particle by particle 

 and partly of the limestone lenses and pieces that appear to have been 

 deposited in small masses. 



CONDITION OF THE SHALE ON THE SEA-BOTTOM 



On the floor of the sea all appears to have been hard or solidifled ex- 

 cepting the newest mud and new lumps of lime on its surface. There is 

 at least no good evidence that the sea-floor was muddy. Even the fossil 

 bivalves, the Pelecypoda are not of the kind here that necessarily bur- 

 rowed in mud, but all are referable to either Anisomyaria — such as live 

 anchored, or to Taxodonta — such as could presumably flatten the foot 

 and crawl on firm surfaces as the living Nucula is said to do. The 

 Brachiopod Lingula occurs also, as said, chiefly in the limey lumps, into 

 which it could burrow while those were fresh, not yet consolidated. 



FUCOIDS 



An apparent objection to the view that the sea-floor was hard should 

 be explained here. There are many fossils, such as might be at present 



^ R. C. Wallace : Pseudobrecciatlon in Ordovician limestone in Manitoba. The Journal 

 of Geology, vol. 21, 1918, p. 402. 



« Thomas C. Brown : The origin of certain Paleozoic sediments. The Journal of Geol- 

 ogy, vol. 21, 1913, p. 232. 



