Reviews — Harder'' s Petrolog;/ for Students. 45 



three in the other. In each case, though the series of segments is 

 not complete either at heginning or end, they are characteristically 

 like those of Echinocaris, the distal edges bearing tubercles, the 

 equivalents of spinules. 



§ XII. 1896. Garyocaris. — In the Journal of Geology, Chicago, 

 vol. iv, 1896, p. 85, Dr. E. R. Gurley has described Garyocaris as 

 the " lateral appendages " of the " polypary " of a Graptolite ! 

 Garyocaris was referred to by us in the First and Seventh Eeports 

 (for 1883 and 1891), and was described in detail and figured in the 

 " Monogr. Brit. Pal^oz. Phyllocarida," Pal. Soc. 1892, p. 89 et seq., 

 pi. xiv, figs. 11-18. 



§ XIII. 1897. A new locality in No.va Scotia has been deter- 

 mined by Sir William Dawson for Estheria Daivsoni, namely. East 

 Branch, East River, Pictou County, Lower Carboniferous. Several 

 casts and impressions of small valves, not more than two millimetres 

 long, occur on the bed-planes of a dark-red Lower Cai'boniferous 

 shale. Former occurrences of this species were noticed in our 

 Report (Eleventh) for 1894. 



S, S ATI IE "W S. 



Petrology for Students : An Introdtjotion to the Study 

 OF Rocks under the Microscope. By Alfred Barker, 

 M.A., F.G.S. Second edition, revised. 334 pp., 75 figs. (Cam- 

 bridge : Messrs. C. J. Clay & Sons, 1897. Price 7s. Qd.) 



THE appearance within two years of a second edition of so 

 excellent a textbook as Harker's "Petrology for Students" is not 

 a subject for surprise. In this revised edition the author states that 

 he has endeavoured to profit by the ci'iticisms of reviewers and 

 private friends. The slight alteration, however, which the book has 

 undergone shows hov/ little cause for adverse criticism there was 

 in the first edition. In general plan and scope the book remains 

 precisely the same. Only about thirty pages have been added, and 

 these are mainly due to the introduction of descriptions of American 

 examples among the igneous rocks, one result of which is, that the 

 reader makes the acquaintance of a number of those new names 

 (Absarokite, Banakite, Carmeloite, Shonkinite, etc.) to the invention 

 of which American geologists have of late been perhaps a little too 

 prone. 



The method of classification of the igneous rocks remains 

 practically the same, but Brogger's name " hypabyssal " is sub- 

 stituted tor "intrusive." As the author remarks, "petrology has 

 not yet arrived at any philosophical classification," and certainly the 

 attempt to pigeonhole the igneous rocks, both basic and acid, into 

 the three groups, jjlutonic, hypabyssal, and volcanic, involves 

 inconsistencies which are evident in the text. Thus three chapters 

 intervene between the descriptions of such similar rocks as the 

 pitchstones of Arran and the " pitchstones " (or, as the author 

 prefers to call them, the Permian rhyolites) of Meissen ; while the 



