212 



CORRESPONDENCE. 



FORAMINIFERA OF THE ChALK AND OF To-DAY. 



After careful perusal of the criticism of my paper on Oceanic Deposits 

 Ancient and Modern (Natural Science, vol. vii. ; Oct., 1895), by Messrs. Burrows and 

 Holland, I am forced to the conclusion that they have failed to grasp both the spirit 

 and the substance of the hypothesis I had intended to suggest, and your insertion of 

 these remarks may perhaps be of service in more clearly defining its scope and aim. 



My object was partly to answer a very valid objection raised by Mr. Philip 

 Lake {Science Pyogress, Feb., 1894) to a certain point in my paper on the " Genesis of 

 the Chalk," and my study of the subject led me to the conclusion that the association 

 of a number of forms in the lower beds of the Upper Cretaceous, and also the asso- 

 ciation of apparently identical forms in certain areas at the present day, notably at 

 Culebra Island, could scarcely be accounted for except on the assumption that in 

 both cases similar conditions had existed. On p. 271, par. 3, I endeavoured to show 

 that this connection was a very close one, and cited, in support of this statement, the 

 presence of various species, ten in all, including the Textularias and Verneuilinas ; 

 the fact of these forms being found separately in other areas, a fact of which I am 

 perfectly aware, does not, to my mind, invalidate the interest of their occurrence all 

 togetkei' only in certain limited positions. 



The authors remark : " T. tvochus is plentiful in the waters of many tropical and 

 sub-tropical areas, and is by no means confined to localities having the peculiar 

 ■position assigned by Mr. Hume to Culebra Island." If these gentlemen will turn to 

 a work published by me in 1893 (Chemical and Micro-Mineralogical Researches, etc.), 

 they will find on p. 17 that I remarked, respecting this actual form : " At the present 

 day it is common off our own shores, but, though cosmopolitan, it is more generally 

 restricted to tropical and sub-tropical areas." It will therefore be evident that it 

 was association, and not individual distribution, to which I more specially desired 

 lo draw attention, and upon which, in fact, I based my argument. My reasons for 

 confining my remarks specially to the arenaceous Foraminifera are : (i.) That these 

 were the only ones I could obtain from the method adopted in the examination of the 

 residues from Cretaceous beds. (2.) Because, from the fact of their being arenaceous, 

 they would be the most likely to be affected by the presence of coast lines ; and 

 (3.) Because in all probability they are mainly, if not entirely, non-pelagic. 



Seeing that I had no evidence to prove their existence during Cretaceous times, 

 I excluded from the scope of my observations such irregular arenaceous types as 

 Rhizamniina and Hyperamniina, which have a deep-sea extension of an altogether 

 remarkable character ; the hyaline and porcellanous forms, also, were not intro- 

 duced as association forms, many of them being pelagic, and consequently indepen- 

 dent of coast-line influences or of current-borne material, besides which their 

 general zonal distribution during the Cretaceous period is as yet undetermined. 



I think my critics will pardon me if I point out that it is scarcely fair criticism 

 to detach lines from sentences, and remark upon them, without any statement what- 

 ever that they (together with the context, and only in such connection) form part of 

 a general train of argument. 



They thus make a quotation from p. 273 of my paper : " At the present day the 

 coarse arenaceous Foraminifera are found at depths rarely exceeding 400 fathoms," 

 but make no allusion whatever to the fact that in that very paragraph I closely con- 

 nect the existence of the majority of Arenacea with the areas of terrigenous deposits, 

 a point which, I maintain, is of the greatest im.portance. In their paper they have 

 selected the type of Huplophvaginium as a proof of the deep-sea extension of Arenacea. 

 but entirely ignore that, on page 274, I have made special mention of two species of 

 this same type as extending into greater depths. 



Before writing the paper I made a minute examination of the "Challenger " reports 



