164 
PACIFIC SCIENCE, Vol. XIX. April 1965 
FIG. 21 a. Microciona eurypa (de Laubenfels). Sec- 
tion showing the basal spongin plate with embedded 
acanthostyles and styles. In the embryo traces of Spon- 
gin B are visible. 
tially the position Dendy (1921) advocated for 
lotrochota. 
DISTRIBUTION: North Australia (Ridley); 
Celebes (Thiele); Philippines (Levi); Mar- 
shall Islands; Truk (de Laubenfels). 
SUBORDER MICROCIONIFORMES de Laubenfels 
family microcionidae Hentschel 
GENUS microciona Bowerbank 
Microciona eurypa ( de Laubenfels ) 
Fig. 2 la, b 
Dictyociona eurypa de Laubenfels, 1954, p. 
143, fig. 91. 
OCCURRENCE: Sta. 220 A. 
DESCRIPTION: This species is an encrustation, 
0. 5-0.8 mm thick, extending over both surfaces 
of a shell of Chama sp. 
COLOR: In alcohol, pale brown, between 
(yY-R 8/4) and (yY-R 7/4). 
SURFACE: Macroscopically smooth, granular, 
and minutely hispid under low magnification; 
no pores or oscules are visible. The dermal mem- 
brane is skin-like and packed with small sub- 
tylostyles. 
SKELETON: A basal plate of spongin, 10-15/a 
thick, supports vertically disposed acanthostyles. 
Long styles, either singly or in brushes, also 
diverge from this spongin plate in which they 
are embedded. Between adjacent spicule brushes 
interstitial styles are abundant, many disposed 
parallel to the substrate. The styles from the 
basal spicule brushes extend throughout two- 
thirds of the thickness of the sponge; secondary 
brushes often arise obliquely from them and 
extend into the densely packed zone of ectoso- 
mal subtylostyles. The latter are arranged in 
brushes with heads inward, but the concentra- 
tion of spicules, of both ectosomal and endoso- 
mal type, obscures the skeletal arrangement in 
the superficial regions of the sponge. The zone 
of ectosomal spicules is 100-125/a deep, the 
external diameter of the spicule brushes is 
100-130/a. 
There is scant development in this species 
of vertical columns of spongin; small localized 
thickenings of the spongin base do occur, how- 
ever. In terms of Levis (I960) work upon the 
skeleton of the Clathriidae, this is a leptocionid 
state. 
SPICULES: Megascleres. (i) Long, thin sub- 
tylostyles, often with asymmetric heads, slightly 
curved or straight, never spined; 237-490 X 
7.5- 13/a. 
(ii) Short, slender ectosomal subtylostyles 
with microspined, often asymmetric heads; 1 12— 
200 X 3.5-5.0/a. 
The smaller subtylostyles of the first category 
are those which occur in the endosome with no 
specific orientation. It is difficult to separate 
these spicules from the larger dermal subtylo- 
styles except that the latter are always termi- 
nally microspined. 
(iii) Short, accessory acanthostyles, evenly 
covered with slightly recurved spines; 80-106 
X 4.0-6.5/a (including spines up to 13.5/a). 
Some extremely small acanthostyles, up to 16- 
25/a, are present; these are probably develop- 
mental stages. 
Micros cleres, (i) Palmate isochelae of two 
distinct size groups: large, 13.5-18/a; small, 
3.5- 5.0/a. 
(ii) Toxa of considerable size range, the 
larger tending to be very slightly flexed and 
resembling raphides, the smaller moderately 
curved with slightly reflexed tips; 36-181/a 
(86/a) and less than 1.0/a in diameter. 
The sponge contains embryos at a late stage 
of segmentation; these are localized just above 
the spongin base and occupy approximately half 
