Reviews — E. Dale's Peak of Derby shwe. 89 



Ostracoda are also present with tliem. The tests of the Ganlt 

 Foraminifera have been but little altered in fossilization, and they 

 differ but slightly in appearance from those in recent deep-sea 

 deposits. MoUuscan shell fragments and prisms occur in all 

 Oaults, but siliceous organisms such as sponge spicules are rare. 

 Mr. Chapman has estimated the mean depth of the Lower Gault sea 

 at 830 fathoms and that of the Upper Gault at 866 fathoms, basing 

 his conclusions on the Foraminifera, but Mr. Jukes-Browne considers 

 these estimates to be excessive. The Gault, on the whole, bears con- 

 siderable resemblance to the Blue and Green Muds of modern seas. 



Typical Malmstone is shown by Mr. Hill to consist principally of 

 colloid silica with usually a small proportion — 10-12 per cent. — 

 •of quartz sand ; other varieties are more or less calcareous. Besides 

 quartz sand, mica and glauconite are present in varying amounts. 



The characteristic organic remains of the Malm and Firestone 

 (Gaize), and also of the beds and nodules of chert, are tlie detached, 

 microscopic spicules of disintegrated siliceous sponges, of which these 

 rocks are mainly composed. In the Malmstone the spicules are 

 mostly of colloid silica, but in the cherts they are generally of 

 ohalcedonic and crystalline silica. Frequently the spicules are 

 partially or entirely dissolved, leaving minute empty hollows, and 

 the rock is then of a light porous character. The dissolved silica 

 «f the spicules is, in the Malm rock, often deposited in the form of 

 very minute globules or discs, in the cherts it forms a hard glassy rock. 



The occurrence of such thick and widely extended masses of 

 Malmstone in the zone of Am. rostrntus and of the chert layers and 

 «aodules in the highest part of the Upper Greensand in the so-called 

 zone of Pecten asper, both largely derived from the remains of siliceous 

 sponges (they have been termed Sponge-beds by Hinde), forms the 

 most striking feature of the Selbornian stage. 



In Chapters xxvi-xxix the underground extensions of the Gault 

 and Greensand, as shown by various deep borings in the London 

 and Hampshire Basins and the Eastern Counties, are referred to ; 

 the characters of the equivalent formations in Northern Franco are 

 given, with lists of fossils compiled by Dr. Barrois, Mr. Price, and 

 M. Delatour ; the physical and geographical comlitions under which 

 the Gault and Upper Greensand were deposited are discussed, and 

 the water supply and economic products are enumerated. 



In an appendix critical remarks on some species of fossils are 

 contributed by Mr. E. T. Newton and Mr. A. J. Jukes-Browne, 

 and these are followed by an elaborate and exhaustive list of fossils 

 of the Selbornian, showing the particular zones and indicating also 

 the localities where they occur. 



III. — The Scenery and Geology of the Peak of Dekbyshirb. ^ By 

 Elizabeth Dale, pp. 106 and index, with 16 plates, 16 views, 

 and a map. (London : Sampson Low, Marston, & Co. Price Ss.) 

 '■pHIS is a tall, attractive-looking volume, with numerous illustra- 

 X tions and plates ; the former, however, have had scant justice 

 ■done to them, and the original photographs have suffered much in the 



