61 JOURNAL OF THE 
for the first time to the radial fibrous mineral which he re- 
garded as impure chalcedony, According to Mr. White, the 
fossil forms are enveloped in chalcedony and the small con- 
cretions are made of the same material. 
In 1887, Prof. J. A. Holmes! visited the Sam Christian 
Gold Mine of Montgomery County, N. C., and studied the 
Paleotrochis-bearing rock in the field. Although he had not 
then seen any of the acid volcanic rocks from New England, 
described by Dr. M. E. Wadsworth, or from the South Moun- 
tain region of Maryland and Pennsylvania, subsequently de- 
scribed by Dr. G. H. Williams and Miss Florence Bascom, he 
was of the opinion that the rocks in the neighborhood of the 
Sam Christian Gold Mine were of eruptive origin. Later ob- 
servations have convinced him of the correctness of this view. 
The same opinion is entertained by Messrs. H. B. C. Nitze 
and George B. Hanna,’ who consider the Paleotrochis-bearing 
rocks at the Sam Christian and Moratock Mines as ancient 
acid volcanics, and state that ‘‘it appears highly probable 
that at least some of these siliceous pebbly concretions are 
spherulites.”. Unfortunately in the preparation of their re- 
port time did not permit the authors to study thin sections. 
The specimens which, at the request of Mr, C. D. Walcott, 
the Director of the U. S. Geological Survey, the present 
writer has had an opportuntity to study, consist of a small 
collection’ from Mexico sent by Prof. H. S. Williams, besides 
three fragments about nine inches in diameter sent by Prof. 
J. A. Holmes, who collected them in 1887 at the Sam Chris- 
tian Gold Mine, North Carolina, and from the same place 
several dozen of the original specimens of Paleotrochis major 
and minor collected by Prof. Emmons. Specimens of the 
rock and isolated fossils, excepting those from Mexico, have 
been cut and polished and thin sections prepared for micro- 
scopical study. 
The rock from North Carolina which contains Paleotrochis 
1 Letter to the author Feb. 6, 1899. 
2 North Carolina Geological Survey, Bul. No. 3, pages 37 and 39. 
3 See Prof. Williams’ article, Am. J. Sct., 335, 1899. 
