THE SPONGES OF THE WEST-CENTRAL PACIFIC 35 



as that in xana. In this regard, the latter species appears exceedingly like 

 the Verongias of the West Indies and Mediterranean, which have attracted 

 so much attention for their color change. The appearance of xana and its 

 effect upon the sense of touch are extremely like that of Verongia; but this 

 latter genus is characterized by skeletal fibers, always having a conspicuous 

 central pith and never containing debris. It is noteworthy that in the specimen 

 from Truk (number M. 471) that some of the clear fibers showed definitely 

 such a pith, but these were very exceptional. It may appropriately be said 

 that Thorectopsamma xana takes the place throughout the western Pacific that 

 is filled in many other parts of the world by species of the genus Verongia. 

 It was originally intended to name this species xanthocyana, in view of 

 its color change, this name being derived from Greek words which are sup- 

 posed to mean respectively "yellow" and "blue." Because the genus name 

 is so long, it seems inappropriate also to have a lengthy species name, hence 

 xana is selected as an abbreviation. 



FAMILY DYSIDEIDAE Gray 



GENUS DYSIDEA Johnston 



Dysidea fragilis (Montagu) Johnston 



Text Figure No. 17 



This species is here represented by the following : 

 U.S.N.M. No. 22931, My No. M. 301, collected June 11, 1949, by hand while 

 wading in the lagoon of Ailing-lap-lap Atoll near Bikajela Island. The 

 depth was low tide, and the substrate was dead coral. 



This specimen is incrusting, with lobes, most of them about 7 mm 

 thick. The total amount represents two patches about the size of the palm 

 of one's hand. 



The color in life was dull gray, both on ectosome and endosome. The 

 consistency was spongy : tough while wet, fragile when dry. 



The surface is conulose, with conules about 0.3 mm high and about 

 one conule per each square mm. The surface is rather slimy to the touch. 

 The pores are microscopic and closed, and the same may be said of the 

 oscules. 



Text Figure No. 17. Portion of the fiber of a sponge identified as Dysidea fragilis, X 182. 



