563.129 



III. 



Foraminifera of the Chalk and of To-day. 



TT^E have read with much interest the able and suggestive paper 

 VV contributed by Dr. W. Fraser Hume to the October number of 

 Natural Science, under the title, " Oceanic Deposits Ancient and 

 Modern." We do not propose to deal directly with the main question 

 underlying Mr. Hume's remarks, namely the conditions under which 

 the Cretaceous deposits of Europe were laid down ; but we venture to 

 put forward some considerations upon the evidence adduced by him 

 from the Foraminifera. 



In the first place we observe that Dr. Hume, in dealing with an 

 objection raised to the argument brought forward in his paper on the 

 " Genesis of the Chalk,"' lays down as a general proposition that,. 

 " if a whole group of organisms retains precisely the same aspect 

 throughout long ages, it may well be asked whether similarity of con- 

 ditions during long periods should not be regarded as a determining 

 factor in such a conservation of structure, and whether, therefore, the 

 onus of proving objections to suggestions based on such identities 

 should not lie with the objectors. "^ He does not, however, proceed 

 to discuss the relationship subsisting between the Cretaceous Fora- 

 minifera as a whole and the corresponding fauna of recent seas ; nor, 

 indeed, does he deal with any considerable proportion of the forms 

 found in the Chalk, but confines himself to a limited number of species,, 

 and those for the most part of the arenaceous type. 



As to the general conditions under which arenaceous Foraminifera 

 are found in recent seas, the writer appears to be seriously misin- 

 formed. He states3 : " At the present day, the coarse arenaceous 

 Foraminifera are found at depths rarely exceeding 400 fathoms." 

 This, however, is by no means the case. To take the genus 

 Haplophvagmmm : the " Challenger " Report-^ shows it to be plentiful 

 at great depths, and at least four species have been found at a depth 

 of 3>95o fathoms. We have ourselves recently had the opportunity, 

 through the kindness of Admiral Wharton, F.R.S., Hydrographer to 

 the Admiralty, of examining a large number of marine soundings,. 



1 Pi'oc. Geol. Assoc, xiii., p. 221 ; May, 1894. 



2 Nat. Sci., vii., p. 270 ; Oct., 1S95. 

 '^ Nat. Sci., vii., p. 273 ; Oct., 1895. 



^ Rep. Chall. Zool., vol. ix., pp. 301 et sqq. and p. 775 ; 1884. 



