488 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



of spongin. Fibers not cylindrical and smooth but irregular in out- 

 line, aggregated and anastomosing to form skeletal tracts, which 

 ma}' be compact enough to deserve the name of compound fibers; 

 between such tracts, extensive askeletal areas. 



PSAMMAPLYSILLA KELLEKI. new species. 



Plate 44, fig. 3. 



Togian Bay, Togian Island, Celebes, two specimens. Sponge a 

 branching species ; several long, slender branches rise from a common 

 basal part, the branches fusing here and there at points of contact. 

 Branches up to 160 mm. long, somewhat flattened, tranverse di- 

 ameter 5-12 mm. ; covered with conuli a few millimeters apart, these 

 interconnected by sharp ridges which pursue in general a longitudi- 

 nal course. Surface in these specimens smooth and without aper- 

 tures visible to the eye. Sponge firm and compact but flexible; 

 of a reddish-purple color. 



Very small pores are scattered thickly over the surface; from 

 them fine pore canals lead through the ectosome. Sections show 

 here and there small canals, which yet are somewhat larger than 

 the average pore canal, perforating the ectosome and opening on 

 the surface; one such measured 20-25 tx in width; possibly these are 

 oscular canals. 



There is a thin surface cuticle and a fibrous layer in the deeper 

 part of the ectosome. The mesenchyme is abundant, with many 

 small cells containing pigment. The flagellated chambers are small 

 but vary a good deal in size in the actual specimens, probably in 

 part owing to contraction. They are ellipsoidal and measure 40 by 

 SO ^, 40 by 20 [jl, 36 by 28 fx, and in some places only 24 by 11 ;j.. 

 "When cut crosswise they appear circular. Conspicuous ducts lead- 

 ing to and from them are absent. 



Skeletal fibers predominantly located in the more axial part of 

 body and largely longitudinal, branching and combining to form 

 a skeleton which is most irregular in its distribution; in places it 

 is closely reticular but extensive areas are quite without a skeleton. 

 Some of the fibers extend outward and terminate in the conuli. 

 Such conular fibers diminish in thickness as they reach the surface, 

 and close to the surface may be only 30—10 \l thick although fre- 

 quently larger: somewhat further in. a characteristic conular fiber 

 measures 80-90 jx in thickness. Individual fibers of the inner skeleton 

 are for the most part 120-350 [x thick. 



The ( individual) fibers are very irregular in shape, the same fiber 

 varying markedly in diameter even within a short length. They are 

 abundantly covered with bulbous enlargements or, in places, with 

 more elongated outgrowths. The whole fiber presents the appearance 

 of a body which grows by budding. 



