42 



PORIFERA. I. 



Gcogr. disfr. Fristedt has the species from Spitzbergen from a depth of 2S0 fathoms. 



Note. This sponge shows a particular feature, which I have not been able to interpret witli 

 complete certainty. On one side, the side on which only the pores are found, a large number of 

 excrescences of a more or less regular subglobular or almost globular form are found, sometimes coa- 

 lesced, and forming irregular bodies. The size of these excrescences is from that of a pea to that of 

 a hazel nut. They are quite regularly constructed, fibres radiating from the place of attachment in a 

 fanshaped way to all sides and piercing the surface; and then these fibres are connected to a net by 

 incomplete fibres parallel to the surface; thus this skeletal construction is upon quite the same prin- 

 ciple as that of the sponge itself, and the skin is also provided with pores. These excrescences appear 

 to be due to a worm (a Syllidian?); at all events one or more of these were found in holes in those 

 excrescences that were cut through. 



5. R. hyalina n. sp. 



PI. XI, Fig 8. 

 Erect, leaf-shaped. The dermal iiieiubraiie 'cvithout spiciiles; the ends of the Jlbres projecting, and 

 the surface conseqiteutly finely shaggy. Osciilaf The skeleton a regular network of primary and secon- 

 dary fibres, the fibres 7mispicular. Particular polyspicular longitudinal fibres are found. Spictila are 

 sligtly ciirved. evenly tapering oxea, 0-268 — o-ji""". 



Of this sponge we have only one specimen, which is, moreover, a fragment; but as it shows 

 characteristic differences from the preceding three lamelliform /?r«/VTff-species, I have thouglit it best 

 to describe it. I take the fragment to be the upper part of a specimen, and with regard to the form 

 of this specimen can consequently only be said that it is a thin lamella. The specimen in hand has 

 a height of ay™"", a breadth of 48""", and a thickness of scarcely 2""". The consistency is rather firm, 

 but the leaf is flexible. The surface is smooth and everywhere finely shaggy from the projecting 

 spicules. The dermal meiuhrane is thin and transparent and without spicules; it rests on the skeleton 

 below, and is pierced by the ends of the fibres, so that no dermal skeleton is found. The colour (in 

 spirit) is whitish, and the sponge is hyaline. As to pores and oscnla, this sponge shows other features 

 than the three preceding ones. No oscular canals are found here as those mentioned in the descrip- 

 tions above; on the contrary roundish openings in the dermal membrane are found in large numbers 

 on both sides of the sponge, varying in size between 0-023'"™ ^^^^^ ^^- 0'298™". All degrees of inter- 

 mediate sizes are found, so that it is impossible by means of the size to distinguish between pores 

 and oscula; perhaps the larger ones act as oscula, the smaller as pores'). 



The skeleton is constructed in quite the same way as in the preceding species with the only 

 exception that no oscular canals are found in it; the polyspicular longitudinal fibres are (in the frag- 

 ment in hand) only little conspicuous. The spicules are in the skeletal net and in the polyspicular 

 longitudinal fibres united in the common way by a clear mass of spongin. 



Spicula are oxea; they are evenly pointed and slightly curved, sometimes the curving is some- 

 what more pronounced, and then it is also sharper; the length is 0-268— 03 15"™, but the greatest length 



M The fragment being the upper part of a sponge, it may also be possible that the oscula have not reached so far 

 up, and that fact may be the reason why no oscular canals or distinct oscula are found. 



