180 
FIG. 21b. Myrmekioderma granulata (Esper). ( Myr - 
mekioderma tylota de Laubenfels. Holotype.) 
massive specimen is Ifaluk 594, the dimensions 
of which are 4.8 cm high, 6 cm wide, 3 cm 
thick. 
COLOR: In alcohol, usually pale cream to 
pale yellowish (rY 8/4) overall, occasionally 
with a pink coloration (pR 5/4) in places. 
TEXTURE: Firm, compact; somewhat fleshy 
and crumbly in the endosome. 
SURFACE: In massive and thickly encrusting 
specimens the characteristic pattern of polygo- 
nal tubercles is clearly developed, although not 
necessarily over the whole surface; thinly en- 
crusting specimens do not show this clearly. In 
all cases the surface is finely hispid. None of 
the present specimens is sufficiently well pre- 
served to demonstrate the presence of pores in 
the grooves between the tubercles; these, how- 
ever, show plainly in USNM 22974, the type of 
Neoprosypa aiina de Laubenfels. 
SKELETON: By far the most precise descrip- 
tion of the skeleton of this species is given by 
Dendy (1905) for Acanthoxifer ceylonensis, 
PACIFIC SCIENCE, Vol. XIX, April 1965 
and this applies in detail to the Palau and Ifa- 
luk specimens. The dense cortical or ectosomal 
region is composed of closely adjacent brushes 
of vertically disposed acanthoxeas. Toward the 
margins of the surface tubercles the orienta- 
tion of the spicules changes from vertical to 
oblique. The spicule brushes thin out leaving 
gaps in the ectosomal skeleton corresponding 
with pore cracks; these open below into sub- 
dermal cavities which extend up to 800g below 
the surface. Cortical acanthoxeas project up to 
180/x beyond the sponge surface, rendering it 
hispid, maximally so over the central region of 
the tubercles. 
The endosomal skeleton is basically a con- 
fused mass of acanthoxeas and larger, smooth, 
predominantly diactinal megascleres. At irregu- 
lar intervals the large megascleres are organ- 
ized into tracts originating at the base of the 
sponge and curving outward to the base of the 
ectosome. Small amounts of spongin are asso- 
ciated with these tracts. 
SPICULES: Megascleres. (a) centrally-flexed 
to straight acanthoxeas with exceedingly fine, 
regular spines over the entire spicule, some- 
times more abundant at the ends. Both stylote | 
and strongylote modifications are frequent; the 
oxeas could often be better described as mucro- 
nate strongyles. These spicules are remarkably 
uniform in their range of size and shape in all i 
of the specimens examined. Very slender devel- 
opmental stages are frequent, (b) Long, rela- 
tively thin, smooth oxeas, strongyles, or, less 
frequently, styles, which make up the bulk of I 
the endosomal skeleton. These spicules are fre- 
quently wavy; only in three specimens are 
straight and somewhat stouter spicules the rule j 
( Acanthoxifer ceylonensis; USNM 22059; and i 
Sta. 100). Many spicules of this category have 
either slightly stairstepped or mucronate tips. 
Microscleres. Raphides in loose trichodrag- j 
mata which, in all specimens examined, break 
up when the spicules are boiled in acid. Some 
single raphides occur. The length of these spic- j 
ules is more variable than earlier reports indi- 
cated (Table 11). 
HISTOLOGY: The ectosome is collenchyma- ; 
tous with a slight concentration of spongin A 
at the inner boundary. The endosome is cavern- 
ous, relatively fleshy, containing abundant ! 
