464 NATURAL SCIENCE. Dec. 



pairs of auricles, and two pairs of kidneys," while other details of its 

 anatomy are given. Of course, if this is the case, the author is 

 perfectly justified in retaining it in an Order Tetrabranchiata, 

 although in opposition to the views of recent writers. It is, however, 

 to be hoped that the specimen from which these details have been 

 determined will soon be adequately figured and exhibited before some 

 learned society by preference, the Royal. 



On the whole, the definitions and descriptions are fairly accurate 

 and moderately clear, while the bibliography at the end should prove 

 useful to English students ; but is it not stretching a point to describe 

 the calyx of Apwcvinns as "pear-shaped," when its shape really 

 resembles that of a piece used in the game of draughts ? Still, if 

 there are slips of this kind, and we must admit that we have counted 

 not a few, it is only because the author has attempted an impossible 

 task. It is far more difficult to compile an accurate and intelligible 

 elementary manual than it is to write an elaborate original monograph. 

 Certainly, no one who has not done the latter should ever be en- 

 couraged to attempt the former. 



F. A. B. 



Text-Book of Geology. By Sir Archibald Geikie, D.Sc, LL.D., F.R.S., etc. 



Third edition. Pp. 1,147. London : Macmillan & Co., 1893. Price 28s. 

 Eight years have elapsed since the second edition of this book was 

 published, and the work accomplished during the interval has led to 

 an increase of 155 pages in the volume. Nevertheless, its actual 

 bulk is not perceptibly increased — the paper is excellent, and the 

 illustrations, of which there are thirty-two more than in the last 

 edition, are admirably printed. The author maintains the moderate 

 uniformitarian doctrines which he has hitherto professed, remarking 

 " that the few centuries, wherein man has been observing nature, 

 form much too brief an interval by which to measure the intensity of 

 geological action in all past time." 



Throughout, the work has been revised where needful, and 

 additional references are given to the latest sources of detailed 

 information. On all matters relating to rocks and rock-structure, to the 

 work of modern agents, and the appearances of the rocks in the field, 

 the definitions and descriptions are most lucid. In the matter of 

 palaeontological succession and of the value of organic remains in 

 correlating strata at a distance, the views of the author are not in 

 harmony with those of advanced zonalists. If " strict contemporaneity 

 cannot be asserted of any strata merely on the ground of similarity or 

 identity of fossils," yet practical contemporaneity may in many cases 

 be justly maintained, especially when a similar sequence of " zones " 

 is found to characterise areas widely separated. Zonal subdivision 

 and attempts at very minute correlation may, however, be carried to 

 an extreme degree ; and further research may justify the cautious 

 attitude of the author, who, in comparing the rocks of distant 

 countries, remarks, " all that we can safely affirm regarding them is, 

 that those containing the same or a representative assemblage of 

 marine organic remains belong to the same epoch in the history of 

 biological progress in each area." 



In the portions of the book relating to Stratigraphical Geology, large 

 additions are made to the sections dealing with the pre-Cambrian 

 and older Palaeozoic rocks, and other sections are duly brought up to 

 date by the insertion of new facts and further references. The book, 

 however, is so well known, that we need say nothing more, except to 



