1869.] DR. J.S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 77 
ALCYONCELLUM, Quoy et Gaimard. 
Sponge fistulate ; fistula single, without a massive base. Skeleton 
siliceo-fibrous ; primary lines radiating from the base in parallel 
straight or slightly spiral lines; secondary lines at right angles to 
the primary ones. Oscula congregated, with or without a marginal 
boundary to their area. 
Type Alcyoncellum speciosum, Museum Jardin des Plantes, Paris. 
DactTyLocaLyx Pumiceus, Stutchbury. 
Sponge cyathiform, slightly pedicelled. Surface even. Oscula 
and pores unknown. Expansile dermal system—connecting spi- 
cula furcated, attenuato-patento-ternate, and dichotomo-patento- 
ternate. Dermal membrane—tension-spicula small acerate and 
subequiangular triradiate spicula; retentive and defensive spicula 
acerate or cylindrical verticillately spinous, whorls of spines nume- 
rous and very large; and also attenuato-stellate, very minute, and 
numerous. Skeleton :—rete irregular; fibre stout, irregularly and 
abundantly tuberculated, apices of the tubercles minutely papillous. 
Auxiliary skeleton-fibres more or less rectangular hexradiate, pro- 
fusely spinous, distal terminations clavate, large and numerous. 
Tension-spicula rectangular hexradiate, smooth, long and slender, 
radii subclavate. Retentive spicula trifurcated attenuato-hexra- 
diate stellate ; and spinulo-trifurcated hexradiate stellate, minute and 
very numerous. Gemmules membranous, aspiculous. 
Colour unknown in the living state. 
Hab. Barbadoes (Dr. Cutting), “ Martinique par M. Plée, 1829.” 
Examined in the state of skeleton. 
Stutchbury’s paper descriptive of this sponge was read at the 
Zoological Society, Oct. 26, 1841, and was published in vol. ix. p. 86 
of their Proceedings. A full account of the paper is also published 
in the ‘Annals and Magazine of Natural History,’ vol. ix. p. 504. 
The author describes the sponge as being “formed entirely of silex, 
the reticulate structure of the mass being composed of transparent 
vitreous tubuli without any admixture of keratose or calcareous mat- 
ter.” This is a mistake, as the adult fibres are solid in every por- 
tion of them from the type specimen that I have submitted to micro- 
scopical examination. 
Stutchbury has characterized the species as follows :— 
‘« Sponge fixed, rigid, siliceotis; incurrent canals uniform in size ; 
excurrent canals large, forming deep sinuosities on the outer surface, 
radiating from the root to the outer circumference.” 
In this description the author has reversed the positions of the 
inhalant and exhalant organs, the former being placed on the outer 
surface and the latter on the inner one. 
The whole of these characters appertain only to its outward appear- 
ance ; and the description would serve equally well for several other 
species beside the one to which he has applied it. I have therefore 
thought it necessary to characterize the sponge from its internal 
