1869.] DR. J.S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 331 
The retentive spinulo-quadrifurcate and pentafurcate spicula are 
very numerous, and the numbers of the two appear to be about 
equal. When a power of 700 or 800 linear is applied to them, their 
margins are seen to be regularly and closely crenulated. I do not 
remember to have seen this remarkable character in the correspond- 
ing spicula of any other species of siliceo-fibrous sponges. 
Ipuitron INGAuuI, Bowerbank. 
Dactylocalyx pumicea, Gray, P. Z. 8. 1867, p. 506, plate xxvii. 
fig. 2. 
Sponge cup-shaped. Rigid skeleton—upper or exhalant surface 
with large intermarginal excurrent canals radiating irregularly from 
the centre towards the circumference. Under or inhalant surface 
with short radiating intermarginal canals. Surface even. Oscula, 
pores, and expansile dermal system unknown. Skeleton—fibre stout, 
more or less furnished with scattered warty tubercles. Auxiliary 
fibres abundantly tuberculated, terminating spinulately. Interstitial 
spicula rectangulated hexradiate, large; radii nearly equal, attenuated 
and acutely terminated. Retentive spicula spinulo-quadrifurcate 
hexradiate stellate; terminal radii long. 
Colour in the natural state unknown. 
Hab. St. Vincent's, West Indies (Thos. Ingall, Esq.). 
Examined in the skeleton-state. 
This sponge is figured by Dr. Gray, on the scale of one-eighth of 
its natural size, in plate xxvii. of the ‘Proceedings’ of this Society for 
1867, and is erroneously designated Dactylocalyx pumicea in p. 506 
of the same volume, but without any reference either to its internal 
or external characters, although the latter in J. Ingaldi are strikingly 
different from those of the rigid skeleton of the former, as I have stated 
at length in my description of the surface-characters of Dactylocalyx 
pumiceus, anted p. 77. 
Beside the difference in the surfaces of the rigid skeletons, there are 
such conclusive structural characters in their configurations that, had 
Dr. Gray taken the trouble to compare sections of the two sponges, 
he must have at once seen that they were not only different species, 
but distinct genera as well. 
In the absence of the expansile dermal systems in both sponges, 
they agree in their external forms exceedingly well; but this cha- 
racter is common to so many and such discordant genera and species 
as to be of little or no value in their specific discrimination, even had 
they belonged to the same genus. 
I have been unable to detect any characteristic fragments of the 
expansile dermal system of the type specimen of I. Ingalli. 
The outer or inhalant surface of the sponge is covered in numerous 
places with a thin brown membrane adhering closely to the surface 
of the rigid skeleton, and dipping into and lining the incurrent 
orifices of the sponge. The membrane is completely covered by 
minute spherical vesicles; but I could not detect any imbedded spi- 
cula. From its close adherence to the surface of the rigid skeleton, 
