158 
PACIFIC SCIENCE, VoL XIX, April 1965 
FIG. 19. Pellina carbonaria (Lamarck). Sta. 133. 
maica in an attempt to find characters which 
will serve to differentiate between the West In- 
dian and the Pacific populations assigned to P. 
carbonaria . 
Only minor differences can be found. The 
spicules are consistently larger in the Pacific 
specimens and, as far as is known, these speci- 
mens do not produce the blue-black exudate in 
alcohol that characterises Pellina carbonaria 
from Jamaica. The dermis is more easily detach- 
able in the Pacific specimens than in the Jamai- 
can specimens, but this feature also characterises 
Lamarck’s type from the West Indies (Topsent, 
1930). 
De Laubenfels considered that the Pacific 
specimens which he assigned to P. carbonaria 
were closer to the type description than were 
his specimens from the Tortugas. His suggestion 
was that Lamarck may have made an error in 
the locality of his specimen and that in fact 
Pellina carbonaria (Lamarck) may have been 
from the Pacific. There is, however, no evidence 
to support this contention. A comparison of the 
spicule size and shape characteristics in this 
species from the two areas (Table 3), reveals 
that the Jamaican specimen and the type are 
closely comparable, as are the three Palau speci- 
mens. The differences between the two groups 
are, however, slight. De Laubenfels’ specimens 
from the Tortugas have substantially smaller 
spicules but show the strongylote and stepped 
condition so common in specimens from other 
localities. 
It is difficult to argue on morphological 
grounds that there are two species involved here. 
There are indications that studies of pigments 
could reveal differences which, in conjunction 
with the slight morphological discrepancies, 
would justify the use of a new name for the 
Pacific specimens. Ecological data on this species 
would be a valuable adjunct to morphological 
studies. P. carbonaria in Jamaica inhabits Zost- 
era flats and rarely produces fistules; nothing is 
known of the habitat and range of growth forms 
of this sponge from the Pacific. 
DISTRIBUTION: West Indies (Lamarck); Cu- 
rasao (Arndt); Jamaica (Hechtel); Palau Is- 
lands (de Laubenfels); Freemantle (W. A. ? ) 
(Carter 1882). 
GENUS Siphonodictyon n. gen. 
This genus is established for Siphonodictyon 
mucosa , the type species, and is closely related to 
Pkloeodictyon Carter. It differs notably in lack- 
ing a bark-like dermal region, in the production 
of great quantities of mucus, in the complete 
lack of spongin, in the cryptic habit and in the 
possession of a dermal skeleton represented by 
brushes of oxeas. Phloeodictyon abenans Dendy 
from New Zealand should also be included in 
this genus. 
Siphonodictyon mucosa n. sp. 
Fig. 20 a, b 
OCCURRENCE: Sta. 92 ( Holotype, USMM 
23697), 92 A (three specimens). 
description: The basal portion of the 
sponge fills large cavities in coral and sends up 
several brittle cylindrical tubes which terminate 
in either sieve areas or oscules. Excessive quan- 
tities of mucus are secreted from the basal mass 
and apparently are exuded over the external sur- 
face of the oscular tubes during life. A thick 
layer of jelly-like mucus invests the sponge in- 
side the cavity. It is difficult to be sure that this 
layer is external to the sponge since, in places, 
a crisp layer of tangential oxeas overlies the 
