394 NATURAL SCIENCE. Dec. 1895. 



4. Additional evidence is brought forward to show that molluscan 

 life-provinces were marked out even before these remote periods, 

 and that any subsequent changes have arisen mainly through the 

 variations in climatic conditions, and the alteration in the character 

 of the barriers that separate the marine areas into different well- 

 marked basins. 



This article, then, has attempted to show that the laws governing 

 the distribution of the Mollusca and Foraminifera, even so far back as 

 Cretaceous times, were similar to those now in force, and that conse- 

 quently the deductions from a study of present ocean life may be applied 

 in determining the general features of ancient oceans. If this be con- 

 ceded, a simple comparison of faunas may enable us to determine 

 variation in bathymetric conditions, even where lithological charac- 

 teristics are of no assistance. Thus, tracing step by step the history 

 of an ancient oceanic area, many inquiries may be suggested 

 which can only be answered by researches pursued in the future on 

 well-marked scientific hnes like those of the " Challenger " Expedition 



W. F. Hume. 

 Royal College of Science, 

 London, S.W. 



