10 DR. J. S. BOWERBANK ON THE SPONGIADjE. [Jail. 7, 



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 tljose of the former de- 

 scription ; and their shafts are not rapidly attenuated and compar- 

 atively 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 incon- 

 spicuous. 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, compara- 

 tively 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. Stutchbury). 

 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 my paper " On 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, 18/2, 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 



