weeks.] PALEONTOLOGY, PETROLOGY, AND MINERALOGY, 1894. 99 
Gil Wallace (Alfred II.). The Ice age and its work. 
Pop. Sci. Mo., vol. vliv, pp. 681-689, 781-791, and vol. xlv, pp. 40-50 and 
244-258. 
Describes glacial phenomena of Europe and North America. 
(jlla Ward (Lester F.). Principesetuietliod.es d'etude de correlation 
au inoyen des plantes fossiles. 
Int. Cong. Geol., Compte Rendu, 5th session, pp. 97-109. 
Abstract : Am. Geol., vol. xiv, pp. 334-335 (;} p. ). 
Published iu English in American Geologist, vol. ix, p. 34, and noticed 
in. Bibliography and Index for 1892 and 1893. 
612 [Correlation of clastic rocks.] 
Int. Cong. Geol., Compte Rendu, 5th session, pp. 167-168. 
Gives a brief summary of methods of correlation of rock formations 
by means of fossil plants. 
613 ■ The Cretaceous rim of the Black Hills [South Dakota]. 
Jour, of Geol., vol. ii, pp. 250-266. 
Abstract : Am, Nat., vol. xxviii, pp. 794-795 (£ p.). 
Describes the occurrence of cycads in Cretaceous strata of the Black 
Hills and gives the section of the Cretaceous and Jurassic strata, with 
notes on the fossil plants collected. Discusses the bearing of the facts 
presented on the Lower Cretaceous of North America. 
614 Eecent discoveries of cycadean trunks in the Potomac forma- 
tion of Maryland. 
Torrey Bot. Club, Bull., vol. xxi, pp. 291-299. 
Gives a historical sketch of the discovery of cycadean trunks in the 
Cretaceous strata of Maryland. 
615 Weed (Walter Harvey). The formation of hot-spring deposits. 
Int. Cong. Geol., Compte Rendu, 5th session, pp. 360-363. 
Describes the formation of hot-spring deposits in the Yellowstone 
National Park. 
616 Livingston to Snake Plains. Itinerary, Livingston to Boze- 
man [Mont.]. 
Int. Cong. Geol., Compte Rendu, 5th session, pp. 364-365. 
Describes the geologic structure of this region. 
617 The Laramie and the overlying Livingston formation in Mon- 
tana, with report on the flora by F. H. Knowltou. 
Abstracts: Am. Jour. Sci., 3d ser., vol. xlvii, pp. 404-405; Am. Geol., 
vol. xiv, pp. 391-392. 
Noticed in Bibliography and Index for 1892 and 1893. 
617<6 The glaciation of the Yellowstone Valley north of the Park. 
Abstract: Am. Geol., vol. xiv, pp. 393-394 (i p.). 
Noticed in Bibliography and Index for 1892 and 1893. 
617/; and Iddings (J. P.). Yellowstone Valley, from Livingston 
to Cinnabar. 
Int. Cong. Geol., Compte Rendu, 5th session, pp. 326-335. 
Describes the geology and structure of the region and its glacial 
phenomena. 
