PORIFERA. III. 



105 



towards the apex, and a shorter or longer part may be smooth. The styli vary much in size but 

 they are not divided into two groups. The length is 0-119 0-35 mm and the diameter at the base is 

 0-0140-027""". The styli may vary somewhat in different individuals, in some they are more robust 

 and more coarsely spined than in others, and at the same time the smooth part towards the point is 

 wanting or small. Also with regard to the size there is some variation, the greatest length being in 

 some individuals o-27 mm . 2. The dermal spicules are straight or slightly curved, cylindrical strongyla; 

 they are slightly but distinctly polytylote and the ends are generally very slightly swollen, the 

 swellings being as a rule scarcely perceptible. The length is in all 0-196 0-28 mm , but there may be 

 some variation between the individuals; the diameter is 0-0028 0-005 mm . b. Microsclera are not present. 



This species is characterised towards H. Dujardinii by the size and shape of the acanthostyli 

 and by the polytylote dermal strongyla. 



Locality: Station 6, 63 43' Lat N., 14 34' Long. W., depth 90 fathoms; station 28, 65 14' La t. N., 

 55 42' Long. W., depth 420 fathoms; station 89, 64 45' Lat N., 27 20' Long. W., depth 310 fathoms; 

 further it has been taken at Iceland, depth 54 fathoms; East of the Faroe Islands, depth 160 fathoms 

 (Ad. Jensen, the cruise of "M. Sars" 1902). The localities lie in the Davis Strait, the Denmark Strait, 

 between Iceland and the Faroe Islands and East of the latter. 



47. H. longurius n. sp. 

 PI. X, Fig. 7. 



Incrusting; surface smooth or nearly so, with scattered pore-sieves. Spicula: megasclera; the 

 skeletal spicules acanthostyli with a small or no head, entirely spined or with a smooth apical part, 

 ", not di-vided into two groups; the dermal spicules strongyla 0-22 0-298""". No microsclera. 



This species grows as thin but very extended incrustations on large Balani, on Brachiopods 

 and one specimen on &Pecten; both the Balani, the Brachiopods and the Pecten were living specimens. 

 As the species grows along and round the Balani, it may reach to a greatest extent of not less than 

 75 mm ; the thickness does not reach 0-5""". The colour (in spirit) is yellowish or greyish yellow, in 

 some specimens dark brown or even blackish brown, but probably this latter colour is due to a change 

 produced later. The surface is smooth or at all events only with a few projecting spicules. The 

 dermal membrane is a thin film resting on the skeleton below. Oscula I have not seen, but the pores 

 are arranged in a somewhat interesting way; they are lying in pore-sieves which are generally 

 circular; the sieves are surrounded by a very low wall and they are thus seen as slight, circular, 

 sharply bordered impressions, the borders of which are only a little elevated over the surface; the 

 whole formation is only little conspicuous, and is generally only to be seen when the sponge is 

 half dried; in some specimens I could not detect pore-sieves. The pores are close-lying in the sieve 

 and of an average diameter of 0-04 mm . 



The skeleton. The dermal skeleton is well developed; it consists of bundles and fibres of dermal 

 spicules stretching from the main skeleton to the dermal membrane, the outermost spicules in the 

 fibres are more or less penicillately spread; sometimes the fibres may stretch horizontally below the 

 membrane for some distance. Around the pore-areas the spicules are radiately arranged and they 



The Ingolf-Expeditinn. VI. 3. 14 



