160 
PACIFIC SCIENCE, Vol. XIX, April 1965 
texture: The oscular tubes are brittle and 
incompressible; the body of the sponge is soft 
and gelatinous, easily torn. 
SURFACE: All surfaces are smooth. Oscules 
are large and terminal on some of the erect 
tubes; pores are presumably restricted to the 
sieve ends of the remaining tubes. 
SKELETON: A dermal skeleton is present in 
some areas of the oscular tubes in the form of 
an irregular reticulation overlying the fibres of 
the endosome. The meshes of this dermal retic- 
ulation are 275-500 ■/* from base to apex. On 
the basal portion of the sponge the dermal skele- 
ton is developed as a tangential multispicular 
reticulum, present only in isolated places, exter- 
nal to the mucous layer. 
The endosomal skeleton makes up almost the 
entire wall of the oscular tubes (900-1500/* 
thick). The inner half of the endosome is oc- 
cupied by stout fibres running longitudinally; 
these are 250-375/* across and are connected 
at frequent intervals by stout transvere fibres, 
62-125/* in diameter. 
The spicules are dense enough in some 
places to obscure the fundamental reticular pat- 
tern of the skeleton. Arising from this inner 
belt of fibres are numerous stout spicule brushes 
aligned at right angles to the long axis of the 
cylinder and running to the surface where they 
fan out and support the delicate dermal struc- 
tures. These brushes are 300-750/* long. 
In the basal portion of the sponge the skele- 
ton is somewhat confused and the details of 
structure are obscured by the abundance of 
darkly staining mucus. No spongin is associ- 
ated with the skeleton and spongin A fibres 
appear to be absent from the ground substance 
of the endosome. 
SPICULES: The spicules are stout, abruptly 
pointed oxeas, 194-212 X 8.5-11.5/*. There is 
considerable variation in shape: some are 
straight, some doubly curved or angulate, the 
majority are evenly curved. Styles are occasional. 
FLAGELLATE CHAMBERS : These are abundant 
in the endosome, spherical, 18-20/* in diameter. 
MUCUS PRODUCTION: There is little devel- 
opment of soft tissue in the fistules and it ap- 
pears that the production of mucus is entirely 
restricted to the base of the sponge. Mallory- 
stained sections of this region reveal numerous 
large oval darkly staining cells, 6.0-10/* long, 
aggregated in groups of 10-20. These are prob- 
ably secretory cells, but the preservation of the 
specimens did not permit use of any specific 
mucus stain. 
DISCUSSION: There has been considerable 
confusion in the literature concerning the sy- 
nonymy of Oceanapia Norman, Rbizochalina 
Schmidt, and Phloeodictyon Carter and the rela- 
tionship of these sponges to the Coelosphaeri- 
dae on the one hand and the Haplosclerida and 
Adociidae on the other. Since the genus Siphon- 
odictyon is related to this group of sponges it is 
necessary to attempt to clarify the position. 
Lundbeck (1902), after studying the holo- 
types of Rbizochalina oleracea and R. carrotta, 
was convinced that Rbizochalina should be re- 
served for Schmidt’s original two species and 
that Pbloeodichyon Carter should be used to 
accommodate all species referred to Rbizocha- 
lina by later authors. Rbizochalina possesses 
well developed spongin fibres containing short 
oxeas; in Phloeodictyon relatively little spongin 
Is associated with spicule tracts and the oxeas I 
are larger. Lundbeck separates Oceanapia (type 
species, Desmacidon jeffreysi Bowerbank) from j 
TABLE 4 
SPECIMEN 
LENGTH OF 
TUBES FROM 
BASE TO TIP 
DIAMETER 
OF TUBES 
OVER-ALL LENGTH, 
BREADTH, AND 
THICKNESS OF SPONGE 
THICKNESS OF 
MUCOUS 
LAYER 
Sta. 92 7 
Broken 
0.8 cm 
4.0 X 3.5 X 2.9 cm 
1.0-1. 8 mm 
Sta. 92A 1. 
2. 
3.5 (2.1) cm 
3.2 cm 
2.0 cm 
7.4 (5.2) cm 
0.8 cm 
1. 1 cm base 
0.6 cm tip 
4.5 X 1.5 X 2.8 cm 
1. 5-3.0 mm 
7 This specimen is designated as hoiotype. 
