PORIFER.\. I. 41 



projecting spicules. The dermal mcvibranr is thin and without spicules; it is resting on the skeleton 

 below, and is pierced by the ends of the fibres; no particular dermal skeleton is found. The colour 

 (in spirit) is brown. The porrs and osaila are as in the two preceding species, but may here be 

 more distincth- observed; pores are found in large numbers on both sides, they have a size from 

 0-02 — 0-23'""'. Oscula are only found on one side of the sponge; the\- are present in large numbens, 

 and are round openings in the skeletal net of a diameter of ca. 0-5"""; of the projecting spicules of the 

 surface those that are situated on the margin of the oscular opening, project obliquely over this 

 opening (PI. XI, fig. 2). The oscular opening leads into an oscular canal of the same diameter, which 

 in a chiefly horizontal direction stretches almost throughout the sponge. 



The skeleton is constructed as in the two preceding species, with the only difference that in 

 the present species there are many more and more powerful longitudinal fibres giving the sponge 

 some firmness in spite of the otherwise rather fragile consistency. The base of the sponge consists 

 almost exclusively of these longitudinal fibres that are here more or less coalesced, and consequently 

 the sponge is at the base hard and firm. The spicules of the fibres are as usual cemented by 

 spongin, but not quite imbedded in spongin. From the base the fibres branch up through the sponge, 

 growing thinner in their course, and most frequently several fibres run alongside and intercross in the 

 thickness of the sponge. The other parts of the skeleton have unispicular fibres ; only the fibres issuing 

 in a fanshaped way from the middle towards the surface, may sometimes show a couple of spicules 

 alongside in the outermost part. 



Spicula are oxea; they are evenly pointed and slightly bent or quite straight The length 

 varies between 0-214 — 0-25'"'", but appears most frequently to be 0-238"'''', the thickness is o-oi2 — 0-014'""'. 

 This species, as will be seen, agrees, as to the length of the spicules, with R. parenchyma; but 

 there is, besides the features given in the description, also a difference to be noted in the spicules, 

 these being thinner in R.parciicli\ma than in the present species, neither are they in the latter so 

 hastately pointed nor are they thinner in the middle than towards the ends. 



As I have had a piece of Fristedt's original specimen of R.vetitilabrum, I have been able to 

 decide that the form and size of the spicules, as well as the construction of the skeleton, agree com- 

 pleteU- with his species, and therefore I regard the identification as sure. The only difference is 

 that in the original specimen the oscula and oscular canals are generally a little larger than in the 

 described specimen. The very short description by Fristedt does not afford much hold for the deter- 

 mination; thus he does not mention that oscula are only found on one side. I do not quite under- 

 stand his description of the skeleton; he says: <.The fibres radiating from the middle of the blade, are 

 arcuated towards the surfaces-; by this it would seem that he can only mean the fibres running from 

 the interior of the sponge arcuately and obliquely upward and outward, and piercing the surface, but 

 he continues: «These fibres are multi-spiculated — — ». This, however, is not the case, these fibres 

 are imispicular, only now and then may be found in their outermost part a couple of spicules along- 

 side. On the other hand he does not at all mention the polyspicular longitudinal fibres, for it cannot 

 well be supposed that they are meant in the first quoted sentence, as they have a quite different course. 

 Locality: The species has only been taken in one specimen, station 28, 65° 14' Lat. N., 55' 42' 

 Long. W., depth 420 fathoms. 



The Ingolf-rxpedition. VI. l. 6 





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