4 A\NAL8 NEW YORK ACADEMY OF SCIENCES 



has found an extensive area of deep sea floor raised to 4000 feet above 

 the present sea level. On the southeast coast of Africa, W. M. Davis 

 noticed the truncation by the present shore line of extensive concentric 

 terraces, traceable far inland, which could only mean the down-faulting 

 of a gigantic block of material to bring the shore line into its present 

 state. It will be said at once that some of these changes of level have 

 taken place in zones known to be in incomplete isostatic adjustment, but 

 this is a matter of no moment whatsoever in comparison with the fact 

 that change of level may be found to have occurred in the very areas 

 where the islands under discussion are to be found. Celebes does not lie 

 upon the continental shelf and yet the island has an obviously continental 

 fauna, and Dr. Matthew has told me himself that Celebes has been a 

 source of no small worry to him. Cuba has similarly a large fauna, de- 

 rived from the American continent, although it does not lie upon the 

 continental shelf. Vaughan, a thoroughly conservative observer, believes 

 (in litt.) that Cuba was quite possibly separated, by the down-faulting 

 of blocks of material, from both Haiti and the mainland. Dr. Matthew 

 (in litt.) says: "The fault block theory is of course a very familiar one; 

 its application to continental movements is undoubtedly extensive, al- 

 though it is just now somewhat of a fetish among stratigraphers, as folds 

 were fifty years ago. But on land the great fault blocks are largely com- 

 pensated by erosion, so that they do not involve so extensive a displace- 

 ment of adjoining surfaces as one might at first suppose. Their applica- 

 tion to explain submarine conditions where such compensation does not 

 occur brings them into an ajDparent conflict with isostatic adjustments. 

 Considering that we cannot possibly prove their responsibility for the 

 sudden changes from shallow sea to abyssal depths in an}^ case, I am in- 

 clined to avoid hasty ascription to such features as block-faulting. I have 

 j)assed beyond the stage of immaturity when one is unreasonably certain 

 about things." I can only add that I am as far from being unreasonably 

 certain regarding isostatic adjustments in general as Dr. Matthew is re- 

 garding marine down faults. To the zoologist these geologic problems 

 seem so differently interpreted by different and equally gifted and trust- 

 worthy students that one is inclined to relegate them all to the limbo of 

 where "you pay your money and take your choice." 



Vastly different, however, is the matter of the zoologic evidence pre- 

 sented by the faunas of some islands as indicative of the island's geologic 

 or geographic history. Dr. Matthew lays great stress upon the importance 

 uf the mammalian element in the fauna. Here a word of caution is not 

 amiss, for mammals act queerly upon islands and often have a way of 

 being most strangeh^ absent, as this is the group which has greatest diffi- 



