404 Scientific Intelligence. 



8. ProhUms in General Physics ; by Morton Masitjs. Pp. vi, 

 90. Philadelphia, IQlY (P. Blakiston's Son and Co.).— This little 

 book contains 1000 problems and it covers the entire field usually 

 taught in engineering colleges. The topics that are more impor- 

 tant or lend themselves more readily to treatment by problems 

 have received greater attention than the relatively less important 

 ones ; for example, certain parts of mechanics and electricity 

 have more space devoted to them than optics. The problems 

 under each heading (equilibrium, calorimetry, etc.) are divided 

 into four groups of equal average degree of difficulty. It is, 

 therefore, possible to select four different sets of about 250 prob- 

 lems each, for use in four consecutive years, or with four divisions 

 of the same class in one year. Since the problems in each group 

 increase in difficulty from the first to the last, an easy course can 

 be made out from the first problems in all four sets, and a more 

 advanced course can be based on the last exercises in the groups. 

 Physical constants required for the solution of the problems have 

 been omitted whenever they are given in the tables in A. W. 

 Duff's " A Textbook of Physics." Answers to the problems 

 have not been incorporated in the volume. As far as one can 

 judge, without testing the book with students, the problems 

 seem to have been carefully selected and arranged. The only 

 obvious drawback to the book consists in the unnecessarily small 

 type used in the printing. h. s. u. 



II. Geology. 



1. A monograph of Japanese Ophiuroidea, arranged accord- 

 ing to a new classification; by Hikoshichiro Matsumoto. Jour. 

 College of Science, Imperial University of Tokyo, xxxviii. Art. 2, 

 408 pp., 7 pis., 100 text figs., 1917. — In this excellent work are 

 noted or described the known living species of ophiurians, num- 

 bering 232 species, here grouped into 88 genera. They have been 

 studied from all angles, and on pages 352-365 is also given their 

 geographical distribution. 



Of especial interest to paleontologists working with Paleozoic 

 forms are the following definitions : 



" Subclass I. CEgophiuroida Matsumoto. Ophiuroidea with 

 external ambulacral grooves and without ventral arm plates. 

 Radial shields, genital plates and scales, oral shields, peristomial 

 plates and dorsal arm plates also absent. Ambulacral plates 

 alternate or opposite ; in the latter case, they may often be soldered 

 in pairs to form the vertebrae. Adambulacral plates, i. e., lateral 

 arm plates, subventral in position. Madreporite either dorsal or 

 ventral, often large and similar in shape to that of an asteroid. 



'^ This subclass inostly consists of Palaeozoic forms, and lacks 

 all the fundamental characters by which the recent ophiurans are 

 clearly distinguished from the asteroids. Indeed, the distinction 



