PORIFERA. I. 83 



1892. Biemma Dantzenbergi Topsent, Resultats des Campagn. scient. du Prince de Monaco, Fasc. II, 

 83, PI. Ill, fig. 5, PI. IX, fig. 16. 

 More or less 7 rregularly leaf-shaped. The dermal membrane fhiii, zvilhotit spicules^ resting on 

 spicules spreading in a penicillate zoay and projecting. The snr/ace accordingly finely shaggy. Osciila 

 numerous^ small, only on one side. The skeleton an irregular network of spicules and loose fibres, 

 from which short fibres go vertically to the surface. Spongin zvanting. Spicula : Megasclera long., 

 slender ty lusty li or subtylostyli, o-2o^—o-iS'()"""; microsclera contort sigmata /yofj—o-oj""'K 



Of this specie-s we have no complete specimen, bnt a great many larger or smaller fragments 

 which give, however, mainh" information as to the external form of the species. By far the greatest 

 number of the fragments are plate- or leaf-shaped, and generally somewhat arcuate, often in an ir- 

 regular way; only a few are quite irregular, and then they show a concave and a convex side, being 

 of a somewhat calicular form. The largest specimen has an extent of la"" in one direction by 

 8— g'^m iji the other. A comparison of the separate fragments conveys the decided impression 

 that this leaf-shaped sponge has been spread more or less horizontally; the irregular, somewhat 

 calicular pieces are, no doubt, the middle parts, and by these the sponge has been attached; a 

 single one of these pieces even shows a short stalk, which is seen to have been attached. Then 

 from these middle parts the sponge has extended in a disc-like manner, more or less horizontally; 

 thus, perhaps, it has assumed a very flat calicular form. The before mentioned largest piece 

 conveys the impression of being a cut from about the middle to the edge; if so, this specimen 

 would have been of a diameter of about 20'=™. The thickness varies between about 10 and 3™"; it 

 is greatest towards the middle, and decreases towards the edge; the irregular middle parts ma>- 

 be somewhat thicker. A little specimen from station 89 has a different form, as a very thin in- 

 crustation on a Hexactinellid-skeleton ; this specimen the greatest extent of which is ca. 20'""', I take 

 to be a quite young individual. The surface is quite finely shaggy from the projecting spicules. The 

 consistency is rather firm. The colour (in spirit) varies between >ellow and brown'). The dermal 

 membrane is thin and transparent, and is supported by spicules spreading in a penicillate way, and 

 piercing it. Oscula and pores: Where the surface is quite undamaged and the dermal membrane 

 consequentl)- present, close-set, most frequently circular openings may be seen on one side of the sponge 

 with the naked cN-e, or by means of a magnifying glass; their size is a little varying, generally it is 

 o-5_in>'". The dermal membrane rises a little round these openings, and .shows a circlet of projecting 

 spicules. On the other side of the sponge no openings are seen. The mentioned openings are oscula 

 which accordingly are only found on one .side. When this oscular side is examined under the micro- 

 scope, the openings are seen to be of very different sizes, and they have been measured quite down 

 to 0-029™""; but this fact is obviously only due to a different degree of closing, the fact being that the 

 smaller the opening appears, the broader is the thin membrane that surrounds the osculum and shuts 

 the canal, of which the osculum is tlie excurrent opening. There is, however, some constant difference 

 in the size of the oscular opening, which difference is dependent on the width of the canal. The 



I) K\\ the piece-s from station lo, and most of those from station 89 are ahnost quite black. This fact I suppose to 

 be due to a staining, but as they are not known to have been in spirit together with animals from which they might have 

 got the colour, it would seem that the sponge may sometimes get the black colour in spirit. 



