THE SPONGES OF THE WEST-CENTRAL PACIFIC 



263 



Text Figure No. 184, Map number 1. West central Pacific Ocean, showing the archi- 

 pelagos studied in this treatise. 



water (but not the deeper portion) dissolves the limestone. This is probably 

 the result of rain water, which for a while floats on top of sea water. In 

 other places the limestone shore is flanked by sandy beach, perhaps an 

 older stage in the sequence. 



The outer reefs contain an area more than 100 kilometers north and 

 south and more than 25 kilometers east to west. Within this area are four 

 large islands (Anjaur, Peleu, Koror, and Babeldaub) and hundreds of little 

 ones. This lagoon is often as much as 30 meters deep. It is much wider v/est 

 of the islands than it is east of them. 



The Palaus, together with Yap and some scattered smaller islands, are 

 often called the Western Carolines. In this case, those islands next to be 

 discussed are called, in contrast, the Eastern Carolines. It is 1,500 kilometers 

 from Yap to Truk. 



The Caroline Islands (or Eastern Carolines) have no submerged table 

 reefs as in the Marianas and Palaus. Terraces are absent or at least poorly 

 defined ; but drowned valleys are well developed, as they are not in the Palaus 

 and Marianas. The reefs are living and form barrier reefs in almost the 

 shape of atolls. The climate is pleasantly tropical, with much rain, especially in 

 Ponape. My studies were chiefly in Truk and Ponape, plus one day at the 

 very interesting uninhabited atoll called Kuop. It is interesting to note that 

 certain of the smaller units of the Carolines have become complete atolls. 



Truk is an atoll, or almost an atoll, consisting of a roughly circular outer 

 reef about 60 kilometers in diameter and a number of large volcanic islands 

 in the lagoon. Some of these, such as Moen and Tol (places where I studied 

 sponges), are about 5 or 6 kilometers in diameter. I was not able to get out 



