26 PORIFERA. I. 



with sand, but such incrustations may also be found in the other specimens. The dermal membrane is, 

 perhaps on account of the incrustation, better preserved than in the other specimens, and therefore I 

 have been able to observe pores, which were found to be spread and were measured of a diameter of 

 up to o'oSj""". The membrane is otherwise thin, transparent, and contracts when torn off, as in the 

 other specimens. The principal difference is that the spicules have an average length of o'49'"'" and 

 a thickness of o-oiy'"'" or a little thinner, and thus they are a little longer and thinner than in the 

 t\pical form; but as the spicules in other respects are of quite the same form, the specimen most likely 

 is only a variety of the species, the spicules in one of the typical specimens, as we have seen, already 

 showing a tendency to be a little longer and thinner. The specimen is from a considerabl)- greater 

 depth than the others, viz. 1041 fathoms. 



This species belongs to those Hah'cko/idria-s^tcies most closely allied to the Reiiiera; the feature 

 of the skeleton that the ends of the fibres project through the dermal membrane, is a particular cha- 

 racter of most of the /?^«/^r(?-species, and also the presence of spongin (or a sponginlike substance) as 

 well as the form of the spicules point to the Rcjtiera. The species must however, on account of the 

 loose, irregular skeleton, only consisting of polyspicular fibres, be referred to the genus Halic/toiidria. 



Remarks. In Gronland-Expedition der Gesellsch. fiir Erdkunde zu Berlin, II, i, 1897 Van- 

 hoffen mentions a species by the name of Pachychalina oblonga Arm. Hans., and thus he is of opinion 

 that the Reniera oblonga of Armauer Hansen is a Pachychalina; as will have appeared from the 

 preceding description, the Roiiera oblonga Arm. Hans, is a Halichondria, and the species mentioned 

 by Vanhoffen, is not identical with Halnlioiidrta oblonga A. H., but is a Rc/iicra (see pg. 51). 



7. H. tenuiderma n. sp. 

 PI. X, Figs. I — 2. 

 Ctishzonshafied^ attached^ the surface finely spiiiitlojis from projecting spicules. The dermal 

 ntembranc thin., zoithout spicules^ the ends of the lihres projecting through it. The skeleton consisting 

 of an open and irregular netzvork of fibres. Spicula oxea o-jj — ^-^j""". 



We have this species in only one specimen, plate- or cushionshaped and attached to a frag- 

 ment of a shell of a Buccinide. It has a greatest length of 20'"'", and reaches to a thickness of 7""". 

 The colour (in spirit) is greyish white, the consistency is tolerably firm. The surface is finely spinulous 

 on account of the projecting ends of the fibres. The dermal membrane is a thin, transparent mem- 

 brane without spicules; it is supported bv the ends of the fibres projecting through it. In this mem- 

 brane some round or oval holes are found which are no doubt oscula; they have a diameter of up to 

 jmm. pores, on the other hand, have not been observed. 



The skeleton consists of an open and irregular network; especially it is irregular in the deeper 

 parts of the sponge, but towards the surface it shows distinct primary fibres running more or less 

 perpendicularly on the surface and jjiercing it; these fibres are polyspicular, but with few spicules, on 

 an average 3—6 spicules alongside; while these fibres are distinct and rather regular, the transverse 

 fibres are only represented by spicules found singly and without any regular position, but irregularly 

 spread, so that the network becomes irregular. No spongin has been observed. 



