Geology and Natural History. 483 



sides is unusually full. Thus we find chapters on the stereo- 

 graphic projection, on general optical principles, especially wave 

 motion, on the properties of isotropic media, two on anisotropic 

 media, one on lenses, four on microscopes, one on the use and 

 care of the microscope, three on methods with ordinary light, 

 especially on methods of determining refractive indices, one on 

 microscopical measurements ; then follow a series of chapters on 

 observations in polarized light, with discussions of the phenom- 

 ena produced in crystals, and of the implements to be used in 

 studying and determining them. Determinations of specific 

 gravity, mechanical separation of rock constituents, microchemical 

 reactions, and the preparation of thin sections are each fully 

 treated in separate chapters. This will serve to give a general 

 idea of the ground covered in the volume. There is scarcely a 

 phase of petrographic work, aside from chemical analysis, in which 

 all methods that have been proposed are not here collected and 

 discussed. Especially valuable is the very full bibliography which 

 will enable one to consult the original sources from which the 

 material has been gathered. The book is well written and the 

 numerous figures helpful ; it is well printed and bound, and 

 while the public to which it appeals is necessarily small, it will 

 without doubt be greatly valued and used by its members. We 

 commend it as a vade mecum to every working petrologist. 



L. V. P. 



2. A History of Land Mammals in the Western Hemisphere; 

 by William Berryman Scott. Pp. xiv, 693, with frontispiece 

 and 304 text figures. New York, 1913 (The Macmillan Com- 

 pany).— Professor Scott has produced an authoritative account of 

 the fossil mammals of the western world, presented in such a 

 manner as to be fully intelligible to the layman and a source of 

 valuable information to the serious student. There are several 

 introductory chapters on geological and paleontological methods, 

 mammalian classification, and on the structure of the skeleton and 

 teeth, a knowledge of which is so essential to the paleontologist. 

 The succeeding chapters deal with the life histories of the more 

 important mammalian orders, but the zoological sequence is 

 reversed, which makes the book slightly confusing to the 

 systematise The last chapter is philosophical in tone, and 

 emphasizes the exceptional difficulty of mammalian evolutionary 

 problems, which experimental zoology and paleontology by com- 

 bining their resources may eventually solve. 



The book is admirably illustrated by clear anatomical drawings 

 and numerous restorations by Bruce Horsfall and Charles P. 

 Knight, all prepared under the careful supervision of the author. 



r. s. L. 



3. Nomenclature of certain Starfishes ; by A. E. Verrill. 

 (Communicated.) — Asterina. In my Revision of this family* 

 (this Journal, vol. xxxv, pp. 477-485, 1913), the specific name 

 minuta was used for a dubious West Indian species. This name 



* In that article an error occurs in the analytical table of genera, p. 479. 

 Above line 4, from bottom, insert : DD. Interactinal plates without a fan of 

 spines. 



