22 PORIFERA. I. 



4. H. velamentosa Ann. Hans. 

 PL I, Fig. 5. PL IX, Figs. 4—6. 

 1885. Reiiiera velamoitosa Armaner HaiLsen, The Norwegian North-Atlantic Expedition XIII, 4, Tab. I, 

 fig. 10, Tab. \T, fig. 3. 



Formed as erect leaves of an irregular shape, most freqiiejitly triangtilar or sometvhat cordate, 

 that is to say, uarrcnvmg below and zvith a curved upper edge, sometimes of an irregular, very obliqtiely 

 cut off and compressed calicular form. The surface rather smooth. The dermal membrane ivith a 

 spiculation of irregularly spread spicjcles forming here and there an irregular net. Oscula numerous, 

 small, chiefly confined to one side. The skeleton consists of fibres, forming an irregular network, longi- 

 tudinal fibres are especially conspicuous. Spicula oxea o-^8 — oyV""". 



This sponge is formed as lamella; of different forms and thicknesses. Most freqnenth' the 

 form is somewhat triangnlar with a cnrved upper edge and the sides converging downwards; they 

 seem to have been attached by the lower part, bnt here they have been broken off. The largest 

 of the specimens, whose form is irregular, has a height of 16'^"', a breadth of 14"", and a thickness 

 of ca. 4'='". Besides the more or less regularly formed lamellse, there are found in the material 

 some fragment.s, a few of which seem to suggest that the lamelke may be drawn out to a stalk down- 

 ward. Two of the least damaged specimens are of an irregular, very obliquely cut off and compressed 

 calicular form, and have certainly had a short stalk; this form is, perhaps, the normal form of 

 the sponge. These two .specimens have a height of 9 — lo''"', a breadth of 8 — 9'^^'", and the wall has a 

 thickness of 1-5 — 2"". The surface is rather smooth, but has more or less conspicuous, irregular folds 

 and swellings. The colour (in spirit) is dirtily grayish brown or brown. The dermal membrane is 

 easily separable from the tissue below, and is provided with a rather close spiculation of irregularh- 

 spread spicules forming, however, here and there an irregular net. Oscula are present in great num- 

 bers, they are small, round or oval, of a size of from ca. a-a™'" down to o-s""". Most frequently the 

 dermal membrane surrounds the oscular aperture as a little, higher or lower cone; in some places 

 oscula are close-set in groups, in other places spread. The pores are situated in the dermal membrane 

 in the intervals between the spicules, sometimes ver}- close-set; their measured sizes vary between 

 0-023 — o'ly"^'". As in man\- leafshaped sponges, oscula seem also here to be found chiefh- on one side 

 of the sponge, and the pores on the other, but this feature is, however, far from being strictly carried 

 through; on the side chiefly provided with pores, groups of oscula and spread oscula may be found, 

 and on the other hand a few pores may be seen on the oscular side. 



The fibres of the skeleton are rather well marked, and form an irregular network; longitudinal 

 fibres are especialh- marked, and may reach a considerable thickness and firmness. 



Spicula are oxea, they are evenly and rather gradually tapering, but not to so high a degree 

 as in H. panicea; they are .slightly curved or more rarely straight; the length varies between 0-58— 

 0-8'""', but is most frequently ca. 075'"'" with a thickness of 0-017'"™. Shorter and finer oxea are onh- 

 seen singly. A few styli are found, which seem especialh- to occur in the dermal membrane; in this 

 strongj'la may also be found quite singh-. 



As I have had a piece of one of the specimens of Armauer Hansen, I have been able to 



