PORIFERA. II. m 



Artemisina suberitoides Vosmaer, Bijdrag. tot de Dierk., 12. Aflev., 3. Gedeelte, 25, PI. I, fig. 16,. 



PI. V, figs. 51—55. 

 1887. Artemisina suberitoides Fristedt, Vega Exp. vetensk. Iakttag. IV, 430, PL 24, figs. 15—17. 

 1887. — Ridley and Bendy, Chall. Rep. XX, Monaxonida, 112. 



Cushion-shaped, roundish, or higher, so that the form becomes, irregular, often somewhat com- 

 pressed cylindrical. The consistency like that of a Suberites. The surface very finely and densely 

 shaggy. The dermal membrane a thin film supported by close-set, somewhat penicillate bundles of 

 dermal-spieules. Oscula a little spout-shaped, placed especially on the upper surface, but also scattered 

 singly round on the sponge. The skeleton in the interior of irregular halichondroid structure, at the 

 surface forming fibres that pass towards the surface and end in the penicillate, projecting bundles of 

 dermal spicules. Spicula: Megasclera subtylostyli of two forms, larger ones 0-45 — 0-65""" in the main 

 skeleton, smaller fusiform ones 0'2p — 07 in the dermal bundles; microsclera of two forms, isochelce pal- 

 mater o-ooy — <ro/_>A'""", fo.xa with spiued ends o-oj — o m j2 



~,mm 



This species, which in its exterior form reminds somewhat of a Suberites, is formed as a more 

 or less high cushion, and has a roundish, more or less oblong contour. One specimen in hand is 

 rather high in proportion to its size, and therefore somewhat irregularly cylindrical. The sponge seems 

 always to grow on a firm underlayer, and we have specimens growing on stones, on Brachiopoda, on 

 shells of muscles and snails, and on Hornera lichenoides. The largest specimen, which is longish, is 

 55 mm long and about 25""" high ; other more roundish specimens are of a similar or smaller size, but 

 often of the same height, so that they become more globular. The smallest specimen has at the base 

 an extent of n""" and is ca. 8 mm high; the mentioned, somewhat cylindrical specimen has a breadth 

 of i2 mm and a height of iy mm . The consistency is firm, about as in Suberites. The colour (in spirit) 

 is yellowish white to gray. The surface is very finely and densely shaggy, almost velvety, from pro- 

 jecting spicules. Seen under a magnifying glass the surface presents a finely reticulate appearance 

 on account of the many small close-set subdermal cavities, which shine through and are separated by 

 the projecting spicula-bundles. The dermal membrane is a thin film; it has no special skeleton, but 

 is supported by the close-standing spicula-bundles, which are spread in a somewhat penicillate way 

 and it is pierced by these bundles. It is not, therefore, to be separated by itself. Oscula are circular 

 or somewhat irregular openings surrounded by a more or less projecting, spout-shaped margin formed 

 by the skin. It is not, however, the thin film that has been designated as dermal membrane, which 

 forms this spout by itself alone, but the skin is here thicker, and the fibres supporting the dermal 

 membrane bend into the oscular rim and form a close spiculation of parallel spicules, all with their 

 point towards the oscular aperture. The greatest oscular diameter may be 3 mm ; the oscula are generally 

 found about at the top or middle of the sponge in a number of ca. three to seven, but besides these 

 some, often smaller ones, are frequently found scattered round on the sponge; sometimes also a few 

 groups of oscula may be found; in one of the largest individuals thus eleven oscula are found altogether; 

 on the smallest specimen only one osculum is found. The pores are found in the areas of the skin; 

 they are circular and small; they were measured to a diameter of 0-017 — o - 048 mm . 



The skeleton. In the inner part of the sponge the skeleton has an irregular, somewhat hali- 



