Geslogy and Paleontology. 635 
GEOLOGY AND PALAZONTOLOGY. 
RoMANOVSKY’s MATERIALEN ZUR GEOLOGIE VON TURKES- 
TAN.—Scattered notes of the geology of Central Asia have from 
time to time been given in these pages, but M. Emm. de Margerie’s 
Compte-rendu de publications relatives à la Géologie de l Asie et de 
l Amérique now gives us the opportunity to give a fuller account. 
MM. Mushketoff and Romanovsky, after having explored with 
great thoroughness the possessions of Russia in Central Asia, have 
published a part of their results. The first volume of M. Mush- 
ketoff’s orographical and geological description of Turkestan 
appeared in 1886, while the first number of M. Romanovsky’s 
Materialen zur Geologie von Turkestan was issued in 1880. M. 
Mushketoff considers the natural limits of Turkestan to be as 
follows: the Mougodjar mountains and the plateau of Ust-Urt to 
the west; the Tsungarian Ala-tau, the chains of the Tian-shan and 
the Pamir to the east; the Kopet-dagh and the mountains of Kho- 
rassan to the south ; and the Tarbatagai, Zenghis-tau and the water- 
shed between the Aral and the affluents of the Irtish to the north. 
The space comprised within these boundaries consists of two 
unequal parts, separated by the crest of the Kara-tau: the northern 
part, about one-third of the total area, corresponds to the basins of 
Lake Balkash and of other smaller lakes, while the larger »uthern 
part forms the Turan or basin of the Aral. The latter is divided 
by the Nura-tau into two portions: the basins of the Syr-daria and 
of the Amu-daria, the latter twice the size of the former. The 
reliefs of Turkestan pass from the N. E.—S. W. direction to that 
of N. W.—S. E. by insensible gradations, so that they form 
bundles of folds having their convexity turned towards the south, 
as in the chains of northern India. There are three principal 
groups of folds, the Tarbatagai, the summits of which do not pass 
2500 metres ; the Tian-shan in the centre, with summits reaching 
£ metres, and even 7300; and in the south the Pamir with a 
central crest reaching 4500 to 5000 metres, and with some summits 
of even 8000. Notwithstanding the diversity of the rocks that 
enter into its constitution, the Turanian basin presents a monotonous 
and but slightly varied geological structure, since Cretaceous, Tertiary, 
and post-tertiary deposits cover ninety-five per cent. of the surface, 
the older formations appearing only as masses here and there piere- 
ing the uniform mantle of modern sediments. Above the Palæo- 
Zoic rocks, with a very noticeable uncomformity, lies a series of 
deposits with fossil plants, evidently a prolongation of the plant- 
ring series of Afghanistan, and of the Gondwana group of Hin- 
dostan, During the Jurassic period the Turan formed a great 
island, extending far to the east, where scattered lagoons received 
