Sponges of Hawaii — De Laubenfels 
packed with aspidasters and is about 100 yu 
thick. The endosome is microcavernous and 
confused. 
The skeleton includes oxeas 8 by 500 to 
12 by 420 fjL and tetraxons that might almost 
or quite suitably be called calthrops. Their 
nearly equal rays are 5 by 105 to 15 by 200 g; 
one is often slightly longer than the others 
and might be considered a rhabd but is not 
clearly so. In addition to these definite megas- 
cleres, there are oxeas 3 by 50 g, perhaps also 
megascleres, but probably to be regarded as 
microscleres. There are abundant aspidasters 
in the cortex. These microscleres are less than 
10 g thick, but are 80 g in diameter — irregu- 
larly rounded discs. They are densely covered 
with conical projections, probably homo- 
logous with the rays of asters, but also re- 
sembling the spines on acanthoscleres. 
Finally, eutylasters 15 g in diameter are also 
present. 
This species was described by Dendy 
(1916: 258) from the Indian Ocean, the only 
previous record. The agreement with Ha- 
waiian specimens is amazingly close. 
Plakortis simplex Schulze 
Described in de Laubenfels (1950: 33). 
This species appears to be moderately 
common throughout the Hawaiian Islands. 
I found it at Keaukaha in 1948. 
Plakina monolopha Schulze 
Fig. 17 
This species is represented by U. S. 
National Museum, Register Number 22788 
(My No. H. 87), collected May 17, 1948, at 
Honaunau at a depth of about 1 meter. 
Fig. 17. Plakina monolopha: spicules, from camera 
lucida drawings. A, Triaxon; B, centrotylote oxea; 
C, tetraxon; D, monoloph spicules. (The scale shows 
100 microns by tens.) 
267 
This is a thin crust 0.6 to 0.8 mm. thick, 
drab, soft, and lipostomous. There is little 
ectosomal specialization. The endosome is 
densely fleshy, with canals 100 g in diameter 
perpendicular to the surface and 200 to 500 
g apart. Doubtless in life these ascended to 
minute oscules. 
The commonest spicules are regular tri- 
axons, with rays 3 by 20 to 4 by 24 g. There 
are sagittal tetraxons with two clads about 
this same size, the third clad very small, and 
the rhabd slightly longer. There are oxeas, 
about 4 by 36 g, usually centrotylote. Finally, 
there are the distinctive monoloph calthrops; 
these tetractinellid or pentactinellid spicules 
have three or four simple sharp smooth rays, 
about 3 by 12 g, in one plane, as divergent 
from each other as possible. The odd ray is 
at right angles to them and about as long but 
terminates in about four sharp spines. 
This species was first described by Schulze 
(1880:. 407) from the Mediterranean. It has 
since been recorded from various European 
regions and by Thiele (1898: 28) from Japan. 
It is doubtless cosmopolitan, but neither 
really abundant anywhere nor ever conspicu- 
ous. 
Chondrosia chucalla de Laubenfels 
This species is represented by U. S. 
National Museum, Register Number 22790 
(My No. H. 77). It was collected at Halape 
in 1945 by R. W. Hiatt (His No. II 679). 
This was from lava rock in a tide pool at the 
west end of Keaoi Island, at low tide. It was 
common in this vicinity. 
This is a massive, subspherical sponge. 
The Hawaiian specimens are about 1 cm. 
thick and 3 by 6 cm. in lateral dimensions. 
The color is black as to surface, dark drab as 
to interior. The surface is smooth, shining, 
and slimy. The pores are all closed, but 
oscules, each about 1 mm. in diameter, can 
be discovered in groups of 2 or 3, such groups 
about 1 cm. apart. 
The skeleton of all sponges probably in- 
cludes a greater or lesser amount of non- 
