fauna of the whole Indo-Pacific is urgently needed. Accordingly I have not restricted myself to 

 the materials of the "Siboga", but also redescribed some obscure forms from other sources, 

 from the Leyden and Amsterdam Museum, in order to render my work more complete, and 

 I did not content myself to merely citing and recording, but also tried to make any species 

 better known. Proceeding in this way it is astonishing what a multitude of perhaps small, but 

 really important, facts may be detected in many so-called "known" species. Certainly (and I 

 wish this to be clearly understood) this does not mean the slightest blame to my predecessors, 

 not even to those who nowadays live only in old-fashioned books and, for some generations past, 

 plaved their rol e in the general tragedy of mankind. For it are not only Stebbing's words 

 here chosen as motto, but also those written by this venerable carcinologist on a former occasion, 

 that I cannot refrain from citing, with the utmost approvement : "it can scarcely be regarded 

 as a reproach to the earlier naturalists that they had not prophetic eyes to make them acquainted 

 with the requirements of modern classification. We are perhaps industriously preparing equivalent 

 stumbling-blocks for a future age, which possibly will only care to distinguish species by the 

 internal structure as seen working in. the living animal under the Röntgen rays. But for the 

 difficulty of identifying forms described by our predecessors, we ought not to lay all the blame 

 on the imperfection of the original accounts. It should be shared by the naturalists who some- 

 times in a long succession are content to quote the name of a species, without using the means 

 at their disposal of making it thoroughly well-known. There is a sort of superstition that a 

 new species is worth publishing, but that to deal with one to which some other person's name 

 and some ancient date is attached, is a poor affair, stale and unprofitable". (On Crustaceans 

 from the Falkland Islands. Proc. Zool. Soc. London, 1900, p. 518). 



The "Siboga" material here dealt with is distributed over the families in the following way: 



Hymenosomidae 

 Retroplumidae . 

 Ocypodidae . . 

 Grapsidae . . . 

 Gecarcinidae . . 



Species 

 2 



I 

 18 



43 

 4 



New 



I 

 2 

 I 



I have to thank heartily my fellow-countryman Dr. J. G. de Man, who kindly and 

 readily, in his usual way, assisted me by lending rare memoirs. The help of this excellent 

 carcinologist has been the more appreciated by me, as international scientific intercourse 

 nowadays is reduced to the extreme ! 



Leiden, July 4, 191 7. 



