56 THE VOYAGE OF H.M.S. CHALLENGER. 



few, rather small, on the summits of small oscular tubes at the top of the spono-e. Pores, 

 observed only in the well-defined "pore-zone" above mentioned, here they are very 

 abundant (PL XI. fig. 2a). 



Sl-eleton. — The main skeleton is extremely diffuse and irregular, consisting of an 

 almost unispicular reticulation of stylote spicules with no definite spiculo-fibre. Below 

 the pore-zone there is an irregular dermal reticulation of thickly scattered stylote and 

 tornote spicules. In the pore-zone itself one finds the stylote spicules absent from the 

 dermal membrane, and the tornota coming to the surface in thick brushes. Above the 

 pore-zone comes a low wall of thickly packed, and for the most part vertically disposed 

 tornota (lying parallel with the surface), terminating above flush with the top of the 

 sponge.^ On the top itself the dermal reticulation is of the same character as below the 

 pore-zone {i.e., irregular). 



Spicules. — («) Megasclera; (l) stout, smooth, slightly curved, rather bluntly pointed 

 styli (PI. XXIX. fig. 1), measuring about 0'87 by 0"03 mm., forming the main skeleton 

 and occurring also in the dermal reticulation ; (2) straight, smooth, slightly fusiform, 

 hastately pointed cylincbicals (tornota) (PI. XXIX. fig. la) with rather peculiarly shaped 

 points, size about 0"56 by 0'019 mm., occurring, as usual, at or near the surface, {h) 

 Microsclera ; long, straight, oxeote rhaphides, size about 0"56 by 0'0031 mm., commonly 

 in whisp-like bundles. It seems to us not at all impossible that the rhaphides in this 

 and in other species of Tedania may be in reality only young oxeote (tornote) 

 megasclera; certain it is that they are very different from the " trichodragmata " such as 

 occur in Esperella murrayi, &c. 



This is a very important and well-characterised species ; it is distinguished from all 

 previously known by its external form and the arrangement of the pores in a definite 

 zone. Its stylote spicule is the largest in the genus. It affords a really splendid instance 

 of the manner in which sponges, which are shapeless masses when occurring in shallow 

 water, assume in abyssal depths (in this case 2160 fathoms) a definite, symmetrical 

 external form ; this is its chief interest, for the species of the genus hitherto known, from 

 comparatively shallow water, are, par excellence, amorphous sponges.^ 



Unfortunately there is only one specimen in the collection and that in bad condition, 

 so that we are unable to give any details as to the minute anatomy. 



LocaZ%.— Station 299, December 14, 1875 ; lat. 33° 31' S., long. 74° 43' W. ; 

 west of Valparaiso; depth, 2160 fathoms; bottom, blue mud; bottom temperature, 

 35°'2. One specimen. 



' This arrangement gives rise to a faint vertical striation on the surface of the sponge above the pore-zone {vide 

 fig. 2). It is also present to a less extent just below the pore-zone. 



2 We must make an exception to this statement in the case of Tedania infundibuliformis, nobis, while Tedania 

 massa, nobis, is an amorphous form ranging down to 600 fathoms. 



