Sponges of Palau, I — Bergquist 
137 
Fig. 6b. Psammaplysilla purpurea (Carter). Left, Psammaplysilla kelleri Wilson, holotype. Right, Sta. 60. 
USNM 23708. 
TEXTURE: Firm, rather elastic in some cases, 
stiffer in others. 
SURFACE: Always conulose, but the height 
and spacing of the conules differ with the speci- 
men from few, low, rather rounded projections 
in the thinly encrusting specimen to blunt, tall, 
and abundant in the specimens from Sta. 60. In 
most specimens, conspicuous ridges connect ad- 
jacent conules. The dermis is thick, smooth, and 
with no apparent pores. Oscules are irregularly 
dispersed, oval and 2. 5-7.0 mm in longest di- 
mension. 
The surface of the holotype of Druinella 
tyroeis is conspicuously reticulated between the 
ridges diverging from the conules. This type 
of structure was described by Carter (1881) 
for A. purpurea, but is not well shown in any 
of the Palau specimens. 
skeleton: A reticulation of irregular, con- 
centrically stratified fibres which are themselves 
built up as a reticulum of extremely fine threads. 
In many places irregular lobes arise from the 
fibres. Most authors have given recognizable 
descriptions of the skeleton of this species, none 
better than Keller (1889 ) and Wilson (1925). 
Inclusions in the form of sand grains vary in 
quantity from specimen to specimen. Some lack 
them entirely. Spicule fragments occur sporadi- 
cally. There is a tendency toward the fusion of 
fibres at the base of the sponge, giving the ap- 
pearance of a basal plate; this is, however, not 
well marked in most specimens. The fibres of 
this sponge are composed entirely of the reticu- 
late substance which makes up the pith in other 
verongiid genera. The concentric structure is 
often more compact at the surface and gives 
the impression of an outer, more dense layer. 
The extreme irregularity of the fibres makes 
measurements of little value, but those quoted 
by Wilson (1925) are typical. 
CORTEX: Of variable thickness and composed 
of dense spongin A, broken into patches by the 
numerous pore canals. In specimens where the 
branches are wider the endosome has a more 
