weeks.! PALEONTOLOGY, PETROLOGY, AND MINERALOGY, 1895. 79 
511 Walcott (Charles Doolittle). Algonkian rocks of the Grand 
Canyon of the Colorado. 
Jour, of Geol., vol. iii, pp. 312-330, with geologic map. 
Refers to the existing literature on these rocks, describes their geo- 
graphic position and distribution, and discusses the nomenclature 
adopted. Describes their stratigraphic relations and gives a vertical 
section of the Grand Canyon series. Includes a discussion of the condi- 
tions of their sedimentation, geologic age, and the possibility of cor- 
relating this series with others of similar lithologic character. 
512 Discovery of the genus Oldhamia in America. 
U. S. Nat. Mus., Proc, vol. xvii, pp. 313-315. 
Reviews previous descriptions of this genus and describes Oldhamia 
(Murchisonites) occidens n. sp,, from the shales and slates of eastern 
New York, which are considered to belong either to the Upper Cambrian 
or Lower Ordovician. 
513 Note on some appendages of the trilobite. 
Wash. Biol. Soc, Proc, vol. ix, pp. 89-97, pi. 1. 
Describes the characteristics of antennae found at Rome, N. Y. 
514 Walker (A. E.). Hamilton sponges [Ontario]. 
Hamilton Assoc, Jour, and Proc, No. xi, pp. 85-87. 
Gives notes and figures of sponges from Niagara rocks near Hamilton, 
Ontario. 
515 Walter (Emma). Does the Delaware water gap consist of two 
river gorges? 
Phila. Acad. Nat. Sci., Proc 1895, pp. 198-205. 
Discusses the evidences which indicate that the Delaware River flowed 
in an opposite direction in pre-Glacial times and quotes from other 
descriptions of similar phenomena. 
51G Ward (Henry A.). Preliminary notice of the Plymouth meteorite 
[Indiana]. 
Am. Jour. Sci., 3d ser., vol.xlix, pp. 53-55, two figures. 
Describes the finding of a meteorite at Plymouth, Ind., and gives a 
chemical analysis. 
517 Ward (Lester Frank). The Potomac formation. 
U. S. Geol. Surv., 15th Ann. Rept., pp. 307-397, pis. ii-iv. 
Describes the stratigraphic and paleontologic relations of the several 
members of the Potomac formation in the Atlantic Coastal Plain and 
includes a general description of the fossil floras of these beds and tables 
showing the geographic range of American and foreign species. 
518 Fossil cycadean trunks of North America, with a revision of 
the genus Cycadeoidea Buckland. 
Wash. Biol. Soc, Proc, vol. ix, pp. 75-88. 
Describes specimens recently found in the Black Hills and gives a list 
of papers on the several species of the genus Cycadeoidea Buckland. 
Describes C. jennyana n. sp. 
519 Watts (O. P.). The cause of the movement of glaciers. 
Sci. Am. Suppl., vol. xxxix, p. 16157. 
