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Show 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 corresponding spicula of any other species of siliceo-fibrous sponges. IPHITEON INGALLI, Bowerbank. Dactylocalyx pumicea, Gray, P. Z. S. 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 1. Ingalli are strikingly different from those of the rigid skeleton of the former, as I have stated at length in m y 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 character 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 spicula. From its close adherence to the surface of the rigid skeleton, |
