636 THE AMERICAN NATURALIST. [VOL XXXII. 
beds of graphitic limestone, beds of iron carbonates, and by a 
great thickness of carbonaceous shales, which are represented 
by graphitic schists in the more altered strata. In the Animikie 
rocks on the northern shores of Lake Superior Ingall finds 
abundant carbon, and it is said that in certain mines and open- 
ings rock gas forms to a considerable extent. Also small quan- 
tities of rock may even be obtained which will burn. “ These 
substances must result from the ordinary processes which 
produce rock gas and coal in the rocks of far later age. The 
hydrocarbons which occur so abundantly in the slightly meta- 
morphosed shales of the Huronian about Lake Superior must 
be of organic origin,” and if so, the graphitic schists of the 
same system “are in all probability only these hydrocarbo- 
naceous shales in a more altered condition.” 
As to the fossils actually detected in what are by some 
geologists regarded as Algonkian strata, Winchell has detected 
a Lingula-like shell in the pipestones of Minnesota. Selwyn 
has described tracks of animals in the Upper Huronian of Lake 
Superior. Murray, Howley, and Walcott have discovered several 
low types in the Huronian of Newfoundland, z.e., a mollusk 
(Aspidella terranovica)! and traces of a worm (Arenicolites 
spiralis), the latter said to occur in the primordial rocks of 
Sweden. Walcott reports the discovery in the Grand Cafion 
of the Colorado of the following Precambrian fossils: “A 
minute discinoid or patelloid shell, a small Lingula-like shell, a 
species of Hyolithus, and a fragment of what appears to have 
been the pleural lobe of the segment of a trilobite belonging, 
to a genus allied to the genus Olenellus, Olenoides, or Para- 
doxides. There is also an obscure Stromatopora-like form 
that may not be organic.” 
Here should be noted the discovery, in 1896, of Radiolaria? 
1 Dr.G. F. Matthew writes me as foll ing t d fossil : “ I have 
seen Aspidella terranovica in the museum at ‘Ottawa and doubt its organic origin. 
It seems to me a slickensided mud-concretion striated by pressure. I have so 
similar objects in the Etcheminian olive-gray beds below the St. John grou p.” 
2 Dr. Matthew likewise writes me: “ The arsine ?) rocks of Adelaide, 
South Australia, Mr. Howchin writes to me he now finds to be Lower Cambrian. 
He has found Archzocyathus in them; but this is not vst of Lowest Cambrian, 
as the genus is found in the Paradoxides beds of the South of France.” 
