Geology and Mineralogy. 61 
the Natural History Society of Montreal, May, 1872, published 
in the Canadian Naturalist, vol. vii, No. 1, p. 1.)—There remain 
one point still before leaving this subject. Tt is the gap between 
tioned ; and I had hoped ere this time to have done something to 
ridge it over. I may here state in anticipation of the results of 
sists of a series of calcareous layers connected with each other a4 
pillars or wall-like processes. The layers are perforated wit 
le 
hess. A beautiful collection of these Devonian forms, recently 
shown to me by Mr. Rominger, of the State Survey of Michigan, 
Who has worked out these fossils with great care, fully confirms 
Tentian, through Huronian, C 
tions, down nearly to the close of the Paleozoic. I have no doubt 
that when these successive forms are studied more minutely, they 
will show, like the Trilobites, indications rather of successive crea- 
e 
Somparatively modern geological period. 
