weeks] PALEONTOLOGY, PETROLOGY, AND MINERALOGY, 1895. 85 
559 Winchell (N. H.). Comparative taxonomy of the rocks of the 
Lake Superior region. 
Am. Geol., vol. xvi, pp. 331-337. 
Presents a table showing the classification of the Lake Superior for- 
mations, and compares it with the classification adopted l>y other writers. 
560 The origin of the Archean greenstones. 
Minn. Geol. and Nat. Hist. Surv., 23d Ann. Rept., pp. 4-35. 
Describes the megascopic and microscopic characters of greenstones, 
and discusses the theory of dynamic metamorphism and the greenstones 
as a geologic terrane. This paper is mainly a critical review of a paper 
by Prof. G. H. Williams on " The greenstone schist areas of the Menom- 
inee and Marquette regions of Michigan; a contribution to the subject 
of dynamic metamorphism in eruptive rocks." 
561 and Schuchert (Charles). Sponges, graptolites, and corals 
from the Lower Silurian of Minnesota. 
Minn. Geol. and Nat. Hist. Surv., Final Rept., vol. iii, part i, pp. 55-95, 
pis. F and G. 
Describes species of sponges, graptolites, and corals occurring in Lower 
Silurian rocks of Minnesota, including several new species. 
562 The Lower Silurian Brachiopoda of Minnesota. 
Minn. Geol. and Nat. Hist. Surv., Final Rept., vol. iii, part i, pp. 333-474, 
pis. xxix-xxxiv. 
Gives a brief sketch of the occurrence of brachiopods in the Lower 
Silurian rocks of Minnesota and description of genera and species. 
563 and Ulrich (E. ().). Historical sketch of investigation of 
Lower Silurian in the Upper Mississippi Valley. 
Minn. Geol. and Nat. Hist. Surv., Final Rept., vol. iii, part i, pp. ix-liv. 
Gives a bibliography of Lower Silurian literature of the Mississippi 
Valley. 
564 Winslow (Arthur). Lead and zinc deposits [Missouri]. 
Mo. Geol. Surv., vols, vi and vii, 1894. 
Abstract: Am. Inst. Mg. Engrs., Trans., vol. xxiv, pp . 634-689 and 
932-933, pis. i-iii, figs. 1-17. 
Gives a historical sketch of lead and zinc, a description of their com- 
pounds, and their distribution and conditions of occurrence. Describes 
the occurrence of lead and zinc in foreign countries and in the various 
States of the United States. Describes the physiography and geology 
of the mining regions of Missouri, and includes an account of the devel- 
opment and occurrences of lead and zinc ores in this State. Discusses 
the nomenclature of the formations and describes their distribution and 
structure. Gives lists of fossils collected from the Silurian rocks. In- 
cludes a discussion of the origin of lead and zinc ores and tables of 
production. 
565 The geologic history of Missouri. 
Am. Geol., vol. xv, pp. 81-89. 
Presents a table showing the classification of the Missouri rocks. 
Describes the geologic changes which occurred in Algonkian, Cambrian, 
Silurian, Devonian, and Carboniferous times and the erosion during the 
Mesozoic and Tertiarv eras. 
