274 THE SPONGES OF THE WEST-CENTRAL PACIFIC 



and Cinachyra, grow in sand. A few grew on other living sponges, but this 

 is probably not a typical substrate. Cliona and Aka actually burrow into cal- 

 cium carbonate (often dead coral) and live concealed. 



Sponges occur commonly on vertical surfaces. They do occur on the 

 upper surfaces of horizontal structures but do so chiefly when no other 

 placement is available. This latter is obviously less favorable to their long 

 life than are vertical surfaces. Danger of debris settling on them and occlud- 

 ing their apertures doubtless is involved. Where a cave is so placed that there 

 is a ceiling, that is to say, the under surface of a horizontal structure, this 

 ceiling gives evidence of being better for sponges even than are vertical 

 surface attachments. For this reason, an excellent method of finding numerous 

 sponges (although small individuals) is to keep lifting blocks of dead coral. 

 If the block was settled into sand or mud, no sponges live on its under sur- 

 face. If there was a space of open water between the block or slab, its surface 

 may be nearly covered with sponges. Many of these are mere incrustations, 

 thin as paper, but some are a little larger than that. Throughout the Marshalls, 

 Carolines, and Palaus, the common sponges so placed were of the genus 

 Spirastrella. 



One whole bay in the Palaus, near Malakal Islet, contained only two or 

 three small specimens of Stylotella (which is the most widespread and hardy 

 sponge in Micronesia) and numerous huge specimens of Stellettinopsis. I was 

 unable to find Stellettinopsis anywhere else in the archipelago. The reason for 

 this peculiar distribution is not clear. The bay was relatively exposed, and, 

 therefore, constituted a comparatively poor sponge environment. 



In several localities near Koror, in regions which ecologically I should 

 anticipate as being very favorable for sponges, there were indeed many, but 

 all were of the genus Hiattrochota. It was not clear why other genera were 

 absent. A biologist who could spend months in this interesting area with 

 chemical equipment might find such problems quite interesting and possible 

 to solve. 



Sponges of the Marianas 



The outstanding sponge of Saipan is Stylotella agminata (Ridley) 

 Lendenfeld, which is the most widespread and in terms of aggregate mass, 

 the commonest sponge in Micronesia. At Saipan, however, it was found only 

 in Tanapag Harbor, usually at 2 to 4 meters depth. Its distribution includes 

 the Marshalls, Ponape, Truk, the Palaus, and Australia. 



Near Charankanoa, in depths of less than one meter, in an area of less 

 than an acre, are found the following two species. 



Haliclona streble, new 



Cinachyra porosa (Lendenfeld) Burton. This occurs also in the Mar- 

 shalls, Palaus, and Australia. It is curious to note that C. australiensis occurs 



