26 



have 2-6 rays. Simple cross-sliaped spicules with club-shaped basally smooth 

 and terminally thickened and spined rays predominate. 



Only a single specimen of Hyalonema alcocki was procured. This was cap- 

 tured near the Laccadives in a depth of 2288 m.=1250 fths. 



Hyalonema investigatoris F. E. Sch. 

 Plate YI, figs. 9-17. 



1895 Hyalonema investigatoris P. E. Sch. in Abh. Preuss. Ak. 1894 pp. 37-39, Taf. VII, figs. 9-17. 



In this species, as in Hyalonema alcocki, paradises occur, but I have not 

 been able to find in it true, ordinary amphidiscs, associated with them. The 

 parenchymal microhexactines with curved rays, so common in H. alcocki, are in 

 H. investigatoris also conspicuous by their absence. Unfortunately the only 

 specimen of this species is rather indifferently preserved. I have named it 

 after the ship which collected it Hyalonema investigatoris. 



The specimen has evidently been considerably compressed and crushed after 

 capture. It now appears as a triangular lamella, 85 mm. long, 30 mm. in maxi- 

 mum breadth and 3-4 mm. thick. From the comer, which corresponds to the 

 lower end of the body of the sponge when alive, a tuft of stout spicules, up to 

 500 1^ thick, which are all broken off, arises. This tuft is several centimeters 

 lono-. The lateral margins of the ti'iangular lamella are simply rounded, whilst 

 the terminal margin is composed of two protruding edges which enclose a longi- 

 tudinal fissure lying between them, hke lips. Although the details of its struc- 

 ture are obliterated, I think one may safely assert that this fissure represents 

 the now quite compressed, oscular, terminal face of the sponge. 



The surface is covered with irregular protuberances. Here and there 

 remains of the dermal membrane are attached to it. The marginal fringe of the 

 oscular field has been lost. The whole body of the sponge is clay-coloured with 

 a reddish-yellow tinge. 



The macroscleres are fairly similar to those of Hyalonema alcocki, the micro- 

 scleres however are considerably different. The dermal pinules measure on an 

 averao-e 800 A' in length, thus being about twice as long as those of H. alcocki. 

 Also the rays which form their basal cross are longer and thicker. The loAver, 

 smooth part of the main ray is 10-16 l^ thick and the spines of the distal part, 

 althoufj-h not long-er than in H. alcocki, are much stouter at the base, and arise 

 from an axis of far greater thickness. 



I have not been able to find any macramphidiscs or mesamphidiscs. I do 

 not wish to assert however, that such spicules are entirely absent. Micramphi- 

 discs of the usual shape, with hemispherical terminal discs and 12 marginal 

 teeth, I also sought for in vain. On the other hand paradises of the same shape, 



