478 Reviews — Tlte Johns Hopkins tStudies in Geology. 



before mentioned, the older tin-bearing alliiviura : this must not 

 be confused with the Tertiary volcanic series, comprising many ash 

 cones and necks and flows of olivine-basalt. This formation also 

 gives rise to deep leads by burying old valleys. 



The Bulletin is excellently illustrated by photographs of local 

 scenery and microphotographs of rocks, and is accompanied by 

 a well-printed coloured geological map on the scale of half an inch 

 to the mile. 



The Johns Hopkins University Studies in Geology. 



No. 1. — The Geology of the Corocoeo Copper District op 



Bolivia. By J. T. Singewald, jun., and E. W. Berry. 



pp. 115, with 7 plates. Baltimore, 1922. Price Sl-25. 

 No. 2. — The Geology and Palaeontology of the Huancavelica 



Mercury District. By E. W. Berry and J. T. Singewald. 



pp. 101, with 10 plates. 'Baltimore, 1922. Price $1-25. 



npHESE publications are the first of a series of monographs to be 

 -*- issued by Johns Hopkins University devoted to the presentation 

 of the results of geological investigation in its broadest sense. The 

 first few numbers will give the results of the Williams Memorial 

 Expedition to South America, while later monographs will be of more 

 general character. 



The Corocoro copper deposits have yielded a very large amount 

 of copper and some silver from dej)osits of a peculiar character : 

 namely, from native copper occurring in beds of red sandstone of 

 Tertiary age. Of late years, however, at greater depths it is found 

 that the native metal gives place to sulphides, which have been 

 successfully worked by flotation. The red rocks, including sand- 

 stones, shales, and conglomerates, are divided into two series, the 

 Vetas and the Eamos, whose relationship is still uncertain ; the 

 meagre palaeontological evidence suggests that the Vetas are Pliocene 

 and the Ramos a little younger. The Vetas have yielded 

 representatives of twenty-three species of plants, mainly Dicoty- 

 ledons, including thirteen sj)ecies of Leguminosae. Full descriptions 

 of the plant remains are given in the memoir. 



Although mercury is widely distributed in Peru, the only district 

 with a large output is Huancavelica, which is known to have produced 

 altogether about 56,000 tons of the metal. The region consists of a 

 highly inclined series of fossiliferous Cretaceous sediments, with 

 volcanic rocks of later, probably Tertiary age. The mercury ore, 

 cinnabar, chiefly occurs as disseminations and veins in the Grand 

 Farallon sandstone member of the Cretaceous and in limestones. 

 The limestones have yielded a fairly abundant Upper Cretaceous 

 fauna showing considerable resemblance to the so-called Comanchean 

 faunas of Texas and Mexico, and still more like the Upper Cretaceous 

 fossils of North-West Africa and the Iberian peninsula : about 

 forty forms are described in detail. 



