540 



SCIENCE. 



[N. S. Vol. XIX. No. 48a. 



explicit avowal that his primary concern 

 is with the practical and not the esthetic 

 stifles complaint while it leaves regret. Fortu- 

 nately the splendid series of plates affords 

 material for a study of this character which 

 has never before been available to any one 

 to whom our large museums are inaccessible. 



Filled as they are with descriptive detail, 

 Professor Mason's pages do not lend them- 

 selves to quotation in a notice of this char- 

 acter. The scope of his work has been in- 

 dicated. Suffice it to say that it is a big 

 book and a good book and we are grateful. 

 Livingston Farrand. 



Columbia University. 



The Paleontology and Stratigraphy of the 

 Marine Pliocene and Pleistocene of San 

 Pedro, California. By Ralph Arnold. 

 Memoirs of the California Academy of 

 Sciences, Vol. III., pp. 420, pis. 37, 4to. 

 This memoir is the most important con- 

 tribution to the invertebrate paleontology of 

 the west American Cenozoic that has appeared 

 since the publication of Gabb's ' Paleontology 

 of the California Suri'ey.' The author has 

 worked very carefully over both the stratig- 

 raphy and the paleontology of the marine 

 Pliocene and Pleistocene of California, ob- 

 taining more satisfactory results than have 

 been reached by previous workers in paleon- 

 tology. The field and laboratory work upon 

 which the paper is based occupied the author 

 for a large part of his time during nearly six 

 years and every problem which presented itself 

 has been carefully worked out to the minutest 

 details. The paper was prepared at Stanford 

 University, where the work was carried on 

 under the able supervision of Professor James 

 Perrin Smith. 



The memoir is divided into two main divi- 

 sions: Part I., a general discussion of the 

 stratigraphy, faunal succession and faunal 

 geography; Part II., a purely zoological dis- 

 cussion of the numerous forms represented in 

 the faunas. Over four hundred species of 

 ijttvertebrates were obtained and this large 

 number gives more than ordinary weight to 

 the conclusions drawn by the writer. 



The Pleistocene formations occurring at 



San Pedro have been designated by Dr. 

 Arnold as the San Pedro series. This is 

 divided into an upper and a lower division, 

 which are separated by an unconformity. The 

 fauna of the lower San Pedro includes 247 

 species, of which 12.5 per cent, are extinct. 

 Of this number 64 per cent, of the species are 

 now living at San Pedro, 17.4 per cent, are 

 living only north of San Pedro, 3.2 per cent, 

 only south of San Pedro. The conclusion is 

 drawn that this is a cold-water fauna. The 

 upper San Pedro fauna includes 252 species, 

 of which 9.5 per cent, of the species are ex- 

 tinct. Of this number 68.2 per cent, are now 

 living at San Pedro, 6.1 per cent, only north 

 of San Pedro, 14.2 per cent, only south o'f 

 San Pedro. The fauna of the upper San 

 Pedro series more nearly resembles that found 

 living on the Pacific Coast two or three hun- 

 dred miles south of San Pedro. In other 

 words, this is a warm-water fauna. 



In addition to a careful discussion of the 

 extensive series of species described from San 

 Pedro, the author has studied a large number 

 of other Pleistocene localities on the coast of 

 California and has presented a valuable cor- 

 relation table. 



The author makes an interesting compari- 

 son of the faunas of the Californian and 

 Japanese coasts in Pleistocene time, and has 

 brought out the fact that the relationship 

 was much closer then than it is now. As the 

 lower San Pedro fauna of California is boreal, 

 it is to be supposed that the northern fauna 

 would also push down the Asiatic coast. In 

 addition to this, the presence of a broad sub- 

 marine shelf would make possible the inter- 

 change of species. 



In Part II. of his paper Dr. Arnold has 

 described many new and important species. 

 He has made an equally important contribu- 

 tion in the redescription and figuring of a 

 large number of species which have never been 

 satisfactorily described or figured. This por- 

 tion of the memoir will be of almost as much 

 value to students of recent and Tertiary 

 faunas as it will be to those who interest 

 themselves in the life of the Quaternary. 



The author and the editorial staff of the 

 California Academy are to be congratulated 



