Reviews— Prestwich' s Geological Text-Book. 81 



With the exception of two, apparently extinct, genera (Podocapsa 

 and SaJpingocapsa), all the Jurassic Eadiolarians can be included in 

 the genera set forth in Hasekel's Prodromus Systematis Eadiolarium. 

 As a rule these older forms are more regular, simpler, and somewhat 

 larger than the recent, and they have less adornment and armature. 



The species described are clearly shown in 18 of the accompanying 

 plates ; most of the figures are drawn to the scale of 300 diameters : 

 on plate xix. are figures of plant-spores and other doubtful minute 

 objects met with in connection with the Eadiolarians, and on plate xx. 

 some of the spicules of sponges are figured. These belong to three, 

 if not four, of the principal divisions of siliceous sponges, and 

 include some very peculiar forms. One of these resembles the so- 

 called plumose (Tannen-baum) flesh-spicule of certain recent 

 Hexactinellids, and is the first hexactinellid flesh-spicule which has 

 been discovered in a fossil state. It would have been more satis- 

 factory to know the scale on which the spicules have been drawn. 



One need hardly state that this memoir is a very important addition 

 to our knowledge of the microfauna of the Jurassic strata, and is 

 strong testimony of the patient industry and zeal of the author in 

 discovei'ing these minute organisms from such various sources. We 

 are promised future notices of Eadiolarians from Triassic and 

 Permian strata, which will be looked for with much interest. 



G. J. H. 



III. — Geology, Chemical, Physical, and Stratigraphical. By 



Joseph Prestwich, M.A., F.E.S., F.G.S. In Two Volumes. 



Vol. I. Chemical and Physical. Eoyal 8vo. pp. xxiv. and 



478, with three Chromo-lithographic folding Maps, three 



folding Coloured Sheets of Sections, and 218 Woodcuts. (Oxford : 



At the Clarendon Press, 1886.) 



nMHIS is an epoch marked by the production of geological text- 



J_ books. Year after year, a steady flow of manuals issues from 



the press, and one prophet after another arises, each with some special 



claim upon the attention of teachers and students. 



Among the vast array of really good books the treatise just issued 

 by the Clarendon Press deserves our special notice, coming as it 

 does from the pen of Prof. Prestwich, one of the oldest living exponents 

 of the science, whose papers upon the Tertiary Geology of the South- 

 East of England, of France and Belgium, and upon the Geology of 

 Coalbrookdale, etc., may be found scattered broadcast through the 

 Transactions, Proceedings, and Quarterly Journal of the Geological 

 Society, while others upon cognate subjects adorn the Philosophical 

 Transactions of the Eoyal Society and the pages of the Geological 

 Magazine. 



The volume before us is devoted to Chemical and Physical Geology, 

 and will shortly be followed by a Stratigraphical and Paheontological 

 companion. Three very pleasing features in the present book are 

 the excellency of the paper, the typography, and the illustrations — 

 matters, alas ! too often neglected, but having a most vital importance 

 in the success or failure of a work. Three chromo-lithographic 



DECADE III. VOL. III. NO. II. 6 



