Revleivs — Kai-rer's Geological Basis of Cities. 477 



Limestone ; and I think it very unwise to disturb the present 

 nomenclature without sufficient reason.^ The MS. names of Mr. 

 Robert Etheridge^ require confirmation, and the best waj'^ to do this 

 would be to describe and figure them. The new genera of Professor 

 Nicholson may in the future embrace some few of the ibrms alread}'' 

 described, but we can hardly supersede the clear definitions of 

 Lonsdale's types as given by M'Co}'. In the Lower Ludlow rocks 

 specimens of P. lanceolata, Goldf., often break up, showing the 

 concentrically wrinkled central axis. In the Girvan District — 

 Scotland — at least two distinct species of this genus may be found — 

 P. costellata, M'Coy, and P. dichotoma, Portl. 



(To be concluded in our next Number) 



I^ IE ■^TIIE] AA7" S. 



The Geological Basis of the Chief Cities of Europe. [Der 

 Boden der Hauptstadte Europa's, etc.] By Felix Karrer. 8vo. 

 pp. 68, with 23 woodcuts. (Holder : Vienna, 1881.) 

 ri^HIS is a small, but concise and very useful, compendium of the 

 JL geology of the European cities — Vienna, Paris, London, 

 Brussels, Berlin, St. Petersburgh, and Eome, with their environs, as 

 determined by transverse sections of the great valleys in which they 

 are situated. The water-supply is particularly described ; and the 

 artesian borings at the several places are described geologically, and 

 mostly figured as illustrative sections, besides the cross-sections of 

 the respective basins and valleys. These illustrations have been in 

 many cases supplied by the author's geological friends in the said 

 cities, and their aid is carefully acknowledged as Avell as the other 

 authorities for compiled information. Besides the water supply (by 

 aqueducts and wells), and the health conditions of the cities, the 

 mineral materials of value in arts and manufactures are also noticed. 

 Altogether, this is an excellent work, full of condensed information, 

 and an invaluable manual of the geology of those portions of the 

 important valleys (Danube, Seine, Thames, Senne, Spree, Neva, and 

 Tiber) in which, the great cities have been built. — T. E,. J. 



coI^I^:ESJPOI^^x5^]2^^G:E]. 



THE WEALDEJST OF HANOVER. 



Sir, — In the June Number of the Geological Magazine, pp. 

 281-283, there is a Eeview of the Wealden of Hanover (Die Wealdeu- 

 bildungen der Umgegend von Hannover, von C. Struckmann). 



The monograph, we are told, is a detailed description of the 

 Wealden formation from the beds resting upon the Portland 

 Limestone upwards. The Wealden is divided into three stages, 

 each foi'ming a well-marked horizon of life. " The deepest is the 

 " M tinder or bunte Wealden-Mergel," representing the Purbeck 



> Since wtiting the above I have been able to study, very carefully, the leadiug 

 types of Palajozoic Ptilodicfya. In a future paper on the Family Ptilodictid.e 

 I shall be able to correct many inaccuracies of our ordinary nomenclatiu'e. 



2 Mus. Pract. Geol. iv. 4*0 in Catalogue of Camb. and Sil. Fossils. 



