Geology. 403 



his studies of the New York graptolites above the lower third of 

 the Ordovician. Part 1 was published in 1905. The last of the 

 graptolites are found in the middle Devonian (Hamilton). He 

 discusses 109 Ordovician, 25 Silurian and 11 Devonian forms. 



An interesting table shows the range of the graptolite genera 

 of the United States; this brings out the fact that Dictyonema 

 ranges through all strata in which graptolites occur, but as a rule 

 the genera are short-lived. There are three important outbursts 

 of generic development: (1) the dichograptid type of the lower 

 Ordovician, (2) the dicellograptid-diplograptid of the middle 

 Ordoviciau, and (3) the monograptid of the Silurian. c. s. 



4. Fourth Report of the Director of the Science Division, etc. 

 N. Y, State Museum, Bull. 121, 1908, pp. 203, with many plates — 

 The annual statement of progress in the various science divisions of 

 the NeAV York State Museum is here presented in interesting form 

 by the Director, Dr. J. M. Clarke. A description is. given of the 

 new museum planned, as far as the ground plan is concerned ; 

 the available space will be 80,000 square feet and the exhibi- 

 tion rooms will be lighted from the top. The first American 

 Helianthaster is described as DL. gyalum. The closing paper 

 by the Director on " The beginnings of Dependent Life" 

 describes the " material from the faunas which might illuminate 

 the incipient expressions of dependent life. It is through this 

 avenue only that the problem of the origin of the symbiotic con- 

 ditions which now pervade all nature can ultimately be approached 

 with hope of resolution." c. s. 



5. Mocks and Mock Minerals. A Manual of the Elements 

 of Petrology loithout the Use of the Microscope ; by Louis Y. 

 Pirsso2s t . Pp. v, 414. New York, 1908 (John Wiley & Sons).— 

 Recent progress in the knowledge of rocks has so largely resulted 

 from the development of the various methods of study employing 

 the microscope that modern text-books of petrology have natur- 

 ally been chiefly devoted to them. It still remains true, however, 

 that from many points of view, scientific as well as practical, rocks 

 must be studied by other than microscopic methods, and it is to 

 this important side of the science that the present volume is de- 

 voted ; its appearance will be welcomed alike by teachers, field 

 geologists, and technical men. Such a volume has long been 

 needed, and the author's experience both in teaching and in active 

 investigation has peculiarly fitted him for its preparation. The 

 work as a whole, after two opening chapters of general character, 

 is divided into two parts : the first (pp. 21-131) deals with rock- 

 making minerals, their characters and the methods for their deter- 

 mination ; the second (pp. 132-408) discusses the various types of 

 rocks, igneous, stratified, and metamorphic, closing with a chap- 

 ter on their determination. The style is throughout clear and 

 interesting, and abundant illustrations, largely from original 

 sources, have been introduced ; the half-tone engravings espe- 

 cially deserve commendation for their admirable execution, clue 

 to the fact that they have been printed, not with the text, as is 

 too often the case, but as separate plates. 



