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Show 10 DR. J. S. BOWERBANK ON THE SPONGIADcE. [J development has been fully accomplished, they exhibit the forms represented by figs. 3 and 4. The adult form only is available as a specific character. . , . The small porrecto-ternate spicula must not be confounded with the young state of the large bifurcating expando-ternate ones. They are always much more delicate in their structure ; their ternate radii are projected at a very different angle from those of the former description ; and their shafts are not rapidly attenuated and comparatively short, but in their perfect state are very long and slender. The skeleton-spicula vary to some extent in size, many of them exceeding in length and stoutness the one figured. The large subsphero-stellate retentive spicula are exceedingly few in number; and all that I have seen have a well-defined spheroidal centre, the like of which I have never observed in the numerous minute ones. TETHEA ROBUSTA, Bowerbank. (Plate II.) Sponge subspherical, sessile ; surface even, strongly tuberculated ; tubercles depressed, large, and numerous. Oscula and pores inconspicuous. Dermis coriaceous, very thick, crowded with very large sphero-stellate spicula with short acutely conical radii; dermal membrane obsolete. Skeleton-fasciculi multispiculous, large, closely compacted, expanding at their distal apices to form the corymbose fasciculi of the tubercles of the dermal surface; spicula inequifusi-formi- cylindrical, large and long. Interstitial membranes abundantly spiculous ; retentive spicula of three sorts:-first, of very large sphero-stellate, the same as those of the dermal rind, comparatively few in number, dispersed ; second, small cylindro-stellate, radii rarely attenuated, very numerous; third, minute cylindro-stellate, radii short, distal terminations clavate, very numerous. Colour in the dried state light grey. Hab. Australia (Mr. Stutchburg). Examined in the dried state. I examined this sponge at the British Museum many years since, very shortly after its purchase, with other sponges from Australia, from the late Mr. Stutchbury ; and I figured one of the large sphero-stellate spicula in m y paper " O n the Anatomy and Physiology of the Spongiadse," published in the ' Philosophical Transactions ' for 1858, plate xxv. fig. 15, and also in vol. i. plate vi. fig. 165, of my • Monograph of the British Spongiadse.' On applying to Dr. Gray for the use of the sponge at the British Museum that it might be figured, I was informed on January 11, 1872, by his late brother Mr. G. R. Gray, that the specimen could not be found; I have therefore figured a thin slice of it which was taken from it for microscopical examinations. This affords an excellent sectional view of the most important structural characters of the sponge. I can therefore only describe its general external characters from recollection. It was not, I think, quite perfect, and did not much |
