518 REVIEWS 



generally imply considerable subsidence, though in places this has been 

 superseded by elevation. A brief description of the physical character 

 and geology of each of the island groups, so far as known, comprises the 

 central part of the paper. A bibliography of the subject is appended. 



R. C. M. 



Geology of the Gold Belt in the James River Basin, Virginia. By 



Stephen Taber. Virginia Geol. Surv., Bull. No. VII, 1913. 



Pp. 271, tigs. 23, maps 2, pis. S. 



The gold mines are localized mainly in Goochland and Fluvanna 



counties. Free gold occurs in quartz veins which cut pre-Cambrian 



quartziteSj schists, and gneisses. The gold seems to be associated with 



granite intrusions, possibly of Cambrian age. 



The author suggests that this district illustrates the formation of 

 quartz veins by the force of crystallization. The value of the gold 

 produced in this region amounts to about $0,000.00 per annum. 



T T. Q. 



Pre-Cambrian Algonkian Algal Flora. By Charles D. Walcott. 

 Smithsonian Misc. Coll.; LXIV. No. 2, 1914. Pp. 153, pis. 19. 



Fossil algal flora, produced by blue-green algae, are found in the 

 Algonkian formations of the Cordilleran region. Walcott describes 

 and figures S new genera and 12 new species of algae from the Belt series. 



Before the discussion of the algal remains, there is a discussion of the 

 continental conditions and sedimentation of Algonkian times. From 

 Robson Peak, British Columbia, to Arizona and southern California, a 

 distance of over a thousand miles, there is a marked Algonkian-Cambrian 

 unconformity. Preceding this advance of the Cambrian sea, the 

 Algonkian was a time of continental elevation and of largely terrigenous 

 sedimentation in non-marine bodies of water; also there was some sub- 

 aerial deposition. Marine sediments accumulated along the shores of 

 the continents, but they are now far buried, and evervwhere lost to our 

 knowledge. This unknown marine life, preceding the Cambrian 

 invasion, belongs to what the author calls "Lipalian" time. Red 

 sandstones and shales in the west suggest an arid and, possibly, a cold 

 climate. The thick limestones in the western interior are explained as 

 having been deposited from non-marine waters bv algae. 



T. T. Q. 



