10 
PACIFIC SCIENCE, Vol. IV, January, 1950 
This species formed an extremely thin en- 
crustation, bare’y 100 g thick at the thickest 
unless measured directly at the conules. It 
spread laterally for distances of several cen- 
timeters on the exceedingly irregular surfaces 
of the coral It was possible to dislodge 
postage-stamp-sized pieces with some diffi- 
culty. In life the color was blue-gray, and 
the transparency of the whole sponge was 
noteworthy. The consistency of the flesh was 
softly colloidal, scarcely more firm than raw 
egg white. The fibers were stiffly elastic. 
The surface of this sponge was decidedly 
conulose, with conules 3 to 7 mm. apart and 
about 2 mm. high. Neither oscules nor pores 
could be found in the preserved specimen. 
Doubtless they were almost or quite micro- 
scopic in life, and completely contracted in 
the alcohol or while the encrustation was 
being scraped off. The whole is so thin that 
no distinction can be drawn between ecto- 
some and endosome; specifically there was 
no evident dermis or dermal specialization, 
merely the surface of the protoplasm. 
Doubtless there was a basal plate of spon- 
gin. Certainly at intervals spongin fibers rose 
upward, perpendicular to the base. These 
fibers are of clear amber-yellow spongin with 
a central region that is densely packed with 
spicule fragments and fine sand. 
This appears to be the third time that any- 
one has found this genus, which is separated 
from the somewhat more common Aplysdla 
by the occurrence of a central region in the 
fiber filled with foreign detritus. The first 
was on the north coast of France, as recorded 
by Topsent (1905: clxxxiv). He described 
his discovery as Pleraplysilla minchini. It dif- 
fered from the Hawaiian specimen in being 
opaque and chocolate-brown in color. The 
second occurrence of the genus was recorded 
by George and Wilson (1919: 165) at Beau- 
fort, North Carolina. This species, Pleraply- 
silla latens, was described as colorless, conules 
less than 1 mm. high; the distance between 
conules was not given. In 1946, I spent the 
summer at Beaufort, but was unable to find 
a trace of Pleraplysilla. Of course it is an 
exceptionally inconspicuous sponge. The 
Hawaiian species is set off by color from 
minchini and in color and conule size from 
latens. The specific name selected refers to 
its transparency. 
Hexadella pleochromata new species 
The holotype of this species is designated 
as spirit-preserved specimen, U. S. National 
Museum, Register Number 22748. It was 
collected January 10, 1948, in Kaneohe Bay 
at a depth of between 1 and 2 meters, grow- 
ing on dead coral. It was also collected by 
dredging at 50 meters depth on the opposite 
side of Oahu, in the ocean south of Pearl 
Harbor, on February 19, 1948. 
This species forms a thin encrustation not 
quite 1 mm. thick. In life the color is sulfur- 
yellow, but upon dying it turns purple. The 
consistency is fleshy, modified by the tough 
dermis. 
The surface of this sponge was smooth, 
with scattered openings 25 to 60 g, in diam- 
eter. No distinction between exhalant and 
inhalant openings could be made. 
The ectosome is a tough organic cuticle, 
giving no evidence of cellular nature but in- 
stead is almost certainly suitably called spon- 
gin. The endosome is completely askeletal, 
comprising only the protoplasmic sponge 
structures. The flagellate chambers are large, 
sack-shaped (eurypylous) , 30 by 60 /jl in size. 
Hexadella was established by Topsent 
(1896: 119), like the preceding genus, for 
thin encrustations found on the north coast 
of France. He used two species names, raco- 
vitzai ( the type ) and pruvoti. Both were yel- 
low, the only difference being that the former 
had rose-red tints. The two have long been 
regarded as conspecific but to clarify the 
literature, such reduction to synonymy is 
definitely made here. It is noteworthy that 
racovitzai does not turn purple on dying. The 
critical diagnosis of Hexadella concerns the 
