80 
720 Spencer (Joseph William Winthrop). On the geological and 
physical development of Guadelupe. 
London Geol. Soc, Quart. Jour., vol. 57, pp. 506-519, 1901. 
721 - - On the geological and physical development of Anguilla, St. 
Martin, St. Bartholomew, and Sombrero. 
London Geol. Soc, Quart, Jour., vol. 57, pp. 520-533, 1901. 
722 - - On the geological and physical development of the St. Chris- 
topher chain and Saba Banks. 
London Geol. Soc., Quart. Jour., vol. 57, pp. 534-544, 1901. 
723 Spurr (Josiah Edward). Origin and structure of the Basin 
ranges. 
Geol. Soc. Am, Bull., vol. 12, pp. 217-270, pis. 20-25, 1901. 
Abstract: Science, new ser., vol. 13, p. 98, 1901. 
Describes the structural features of the ranges in the Great Basin 
region and discusses their origin. 
724 - - Variations of texture in certain Tertiary igneous rocks of the 
Groat Basin. 
Jour. Geol., vol. 9, pp. 586-006, fig. 1, 1091. 
Describes the character and occurrence of the variations of certain 
andesitic and rhyolitic rocks and uives chemical analyses. 
725 Stanton (Timothy W.). [Report on Cretaceous fossils from the 
John Day Basin, Oregon. J 
Univ. of Cal., Dept. of Geol., Bull., vol. 2, pp. 280-284, 1901. 
Gives list of fossils with notes on some of the species and discusses the 
faunal relations. 
726 - - Chondrodonta, a new genus of ostreiform mollusks from the 
Cretaceous, with descriptions of the genotpye and a new 
species. 
U. S. Nat. Mus., Proc, vol. 24, pp. 301-307, pis. 25-26, 1901. 
727 Stearns (Robert E. C). Fossil land shells of the John Day 
region, with notes on related living species. 
Wash. Acad. Sci., Proc, vol. 2, pp. 651-658, pi. 35, 1900. 
727a - - The fossil fresh-water shells of the Colorado desert, their 
distribution, environment, and variation. 
U. S. Nat. Mus., Proc, vol. 24, pp. 271-299, pis. xix, xxiv, L901. 
728 Stevens (E. A.). An occurrence of limburgite in the Cripple 
Creek district [Colorado]. 
Am. Inst, Mg. Engrs., Trans., vol. 30, pp. 759-764, figs. 1-4, 1901. 
Describes the occurrence and character of this rock type. 
729 Stokes (H. N.). On pyrite and marcasite. 
U. S. Geol. Surv., Bull. No. 186, pp. 1-50, pi. 1, figs. 1-2, 1901 ; Am. Jour. 
Sci., 4th ser., vol. 12, pp. 414-420, 1901. 
Describes the uncertainty of the methods of distinguishing pyrite and 
marcasite and a method for the quantitative determination of the min- 
erals when in mixture, and discusses the relations of these sulphides to 
those of copper. 
