124 NATURAL SCIENCE [February 



no constant criteria by which Plcurotoma can be separated from 

 Surcula, a state of things which is not surprising to the thorough- 

 going evokitionist. It occasionally happens " that the main features 

 of the sculpture of the adult are foreshadowed even in the proto- 

 conch," but, on the other hand, it is by no means infrequent for 

 them to appear but scantily even in the brephic stage, and then the 

 ornament is usually not of a permanent character, but may be " modi- 

 fied at the caprice of the individual." Hence the author deduces 

 the rule that -when the scheme of ornament appears early in the 

 course of individual development, it is a criterion for the discrimina- 

 tion of species, but when it does not appear till the later neanic stage, 

 and is only completed late in life, it " merely characterises the indi- 

 vidual, and is only of negative use for the purposes of classification." 



In intra multisulcata the columellar plaits in the brephic stage 

 number only two, wdiilst, as the shell grows, they increase to five, 

 whence it is fair to conclude that in this genus at all events 

 their number is not a matter of systematic importance. We might 

 multiply such extracts indefinitely, but the above will suffice to 

 indicate the nature of the work. 



It is not surprising that the author has found it difficult to decide 

 how far the beds from which his specimens came are really homo- 

 taxial with the European strata of the same name. Indeed, in con- 

 sidering the family Volutidae, of which he had large series of larval 

 shells for examination, he definitely states that their development " is 

 much more advanced than one would have expected to find in beds as 

 old as the Eocene." 



The dry but important matter of nomenclature has been con- 

 scientiously studied, and some inevitable alterations in well-known 

 names have been introduced, but Mr Harris is to be commended for 

 the care with which he has given the type of every genus. In conclu- 

 sion, we desire to congratulate Miss G. M. Woodward on the excellence 

 of the plates, and Messrs Stephen Austin & Sons on tlie typography 

 of the volume. W. E. H. 



Soils 



Soils and Sub-soils from a Sanitary Point of View ; with especial reference to 

 London and its neighbourhood. By Horace B. Woodward. Mem. GeoL Survey 

 England and Wales, 1897. Price 2s 6d. 



The Director-General of the British Geological Survey is to be con- 

 gratulated on an important new departure. He has not only issued 

 a small popular handbook relating to Economic Geology, separate 

 from the technical and purely scientific matters with which the 

 Memoirs of the Survey usually deal ; he has also succeeded in breaking 

 through the traditions of the Public Office over which he so worthily 

 presides, and has been able to distribute the valuable little work to 

 the scientific press for review. The typography of the publication is 

 also a great improvement upon most of the works issued from the 

 same office — less battered type and the illustrations carefully printed 

 — while the printing of the map in colours proves eminently 

 successful 



This memoir, as the title indicates, is a practical treatise on soils 

 and sub-soils, with special reference to London, by one of the most 



