THE SPONGES OF THE WEST-CENTRAL PACIFIC 191 



than 1 /x in total elevation and, therefore, easily overlooked. There does not 

 seem to be any localization of the spicule types within the sponge. The micro- 

 scleres consist of trichodragmas of which the individual raphides are about 

 0.3 [.l by 35 fi. 



The specific characters were treated above in connection with the generic 

 description. 



The species name is selected for euphony but was suggested by the fact 

 that it is a popular feminine name among the natives of Ebon Atoll. 



GENUS DENSA de Laubenfels 

 Densa mollis, new 



Text Figure No. 128 



This species is here represented by the following: 

 U.S.N.M. No. 23076, My No. M. 457, here designated as type, collected 

 August 10, 1949, by diver from the vicinity of Moen Islet in Truk 

 lagoon. The depth was 2 meters, and the substrate was dead coral. 



This is an incrusting sponge, 4 mm thick and about 10 cm in lateral 

 dimensions. 



The endosome and ectosome color in life was vivid yellowish brown, 

 and the consistency extremely soft. 



The surface is punctiform, owing to the fact that the pores are often 

 in groups about 1 mm apart and 200 to 300 mm in diameter. In each of these 

 groups, the individual pores are 65 ju, to 130 /x in diameter but are crowded 

 closely together so that the partitions between them are narrower than the 

 width of the pores themselves. The oscules could not be made out as distinct 

 from the inhalant openings. 



The ectosome shows no specialization other than a protoplasmic thicken- 

 ing, and the endosome is in great confusion. 



The skeleton consists of oxeas strewn in utter confusion throughout the 

 endosome with no fibers nor tracts. These are long smooth oxeas, 2 /a by 

 140 jx to 2.5 [x by 137 [x in dimensions. 



Special comment should be made on the relatively enormous quantity of 

 colloidal material in this sponge. In staining material for slides with safranin 

 less than half of the sponge material took the dye stuff at all. Even with 

 haematoxylin, much of this yellow colloid remained quite unstained. 



At the present time there is only one other species in the genus Densa. 

 This is Densa araminta de Laubenfels, 1934, page 14, from the West Indies. 



Text Figure No. 128. Spicule (oxea) of Densa mollis, X 781. 





