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least in many places, cooler. The Pliocene was rather warm but un- 

 doubtedly became colder toward the beginning of the Pleistocene when 

 glacial conditions reached full expression. 



The author concludes that the marked climatic variations of the 

 past are primarily due to periodic changes in the topography of the land 

 surface, modified by the variations in the amount of heat stored in the 

 oceans, and the change in the composition of the atmosphere which 

 conditions the storage of solar radiation. Supplementary notes with 

 quotations from original descriptions of pre-Permian tillites and a bibliog- 

 raphy of the subject are appended. 



R. C. M. 



Oceania. By P. Marshall. Handbuch der regionalen Geologie, 

 5. Heft, Band VII, Abteilung 2. Heidelberg, 191 2. Pp. 36, 

 figs. 10. 

 Oceania, limited on the west by the Marianne, Pelew, and Caroline 

 islands, on the east by the Sandwich Islands, is a region measuring about 

 8,400 miles east and west, and 4,200 miles north and south. Most of 

 the islands are small, aggregated in rather well-defined groups or lines, 

 and within the limits of each group the geological and physical structures 

 are somewhat uniform. With the exception of the largest only, the 

 islands are volcanic or composed of coralline limestone, and almost 

 every island is fringed by coral reefs. The basin of the Pacific is of 

 great, and nearly uniform, depth (2,500-3,000 fathoms), but in the west 

 part of Oceania the ocean depths are far less regular. Very deep troughs 

 are found subparallel to some of the island chains and their connecting 

 submarine ridges, and the location of the shallows and basins is suggestive 

 of important structural relations. The island chains seem to define 

 at least four mountain ranges which are seen to converge toward North- 

 ern New Zealand, a region therefore of great structural importance. The 

 true border of the Pacific basin segment of the earth's crust is marked 

 by a fairly definite line, indicated by the submarine elevations, areas of 

 raised coral rock, and the distribution of andesitic rocks. This line 

 passes through the Kermadec, Tonga, Fiji, New Hebrides, and Solomon 

 islands, and is noteworthy as the belt of present volcanic activity. 

 Triassic fossils in New Zealand and New Caledonia indicate their coastal 

 connection in the past, and the present faunal and floral distribution 

 is strongly suggestive of the former existence of a continental area 

 limited by the island line mentioned. Coral growths of the Pacific 



