112 BIBLIOGRAPHY OF NORTH AMERICAN GEOLOGY, [bull. 27 
Spencer (W. K.). 
1. On the structure and affinities of Pala^odiscus and Agelacrinus. 
Roy. Soc, Proc, vol. 74, pp. .81-46, 1 pi., 12 figs., 1904. 
The investigation described is based in part upon specimens of Agelacrini | 
from the Ordovician of Ohio. 
Spinks (Charles H.). 
1. Magnesite and its uses. 
Cal. Jour. Techn., vol. 4, pp. 68-71, 1904. 
Describes the occurrence and geologic relations of magnesite deposits in soutl 
ern California, and discusses their origin. 
Springer (Ada). 
1. On some living and fossil snails of the genus Physa, found at \a 
Vegas, New Mexico. 
Phila. Acad. Nat. Sci., Proc, vol. 54, pp. 513-516, 1 pi., 2 rigs., 1902. 
Spurr (Josiah Edward). 
1. Preliminary report on the ore deposits of Tonopah, Nevada. 
U. S. Geol. Surv., Bull. no. 225, pp. 89-110, 1 pi. (geol. map), 4 figs., 1904. 
See no. 1158 of U. S. Geol. Surv., Bull. no. 240. 
'2. Ore deposits of Silver Peak quadrangle, Nevada. 
U. S. Geol. Surv., Bull. no. 225, pp. 111-117, 1904. 
Describes the general geology and the character and occurrence of the go 
and silver ore deposits and the mining operations. 
3. Notes on the geolog}^ of the Goldfields district, Nevada. 
U. S. Geol. Surv., Bull. no. 225, pp. 118-119, 1904. 
Describes the general geology and the occurrence of gold-bearing quartz veirji 
4. Coal deposits between Silver Peak and Candelaria, Esmeralc 
County. New 
U.S. Geol. Surv., Bull. no. 225, pp. 289-292, 1904. 
Describes the general geology of the region, the character and occurrence 
the coal, and the outlook for development. 
5. Alum deposit near Silver Peak, Esmeralda County, Nev. 
U.S. Geol. Surv., Bull.no. 225, pp. 501-502, 1904. 
Describes location, occurrence, character, and origin of this deposit. 
6. The Silver Peak region, Nevada. 
Eng. & Mg. Jour., vol. 77, pp. 759-760, 4 figs., 1904. 
Describes the character, occurrence, and origin of the gold and silver o> 
deposits. 
7. Geology applied to mining. A concise summary of the chi< 
geological principles, si. knowledge of which is necessary ii 
the understanding' and proper exploitation of ore deposits f< 
mining men and students. 
New York, The Engineering and Mining Journal, 826 pp., 70 figs., 1904. 
8. Faulting at Tonopah, Nevada. 
Abstract: Science, new ser., vol. 19, pp. 921-922, 1904. 
