28 PORIFERA. I. 



.small, up to a length of 0-47""", and thus the\- belong to the smaller of the spicules occurring in the 

 sponge. The skeleton consists otherwise of large and small spicules lying without any order among each 

 other in every direction, and ver\' closely packed. No fibres are found. The spicules are most closely packed 

 towards the surface, which is, accordingly, \ery hard. Where the surface is smooth, the large spicules 

 inside of the dermal membrane are seen, in a section perpendicular on the surface, to be arranged 

 chiefly parallel to this (pi. X, fig. 6); where, on the other hand, the surface is shaggy from the project- 

 ing spicules, the section shows these, which are all large, to be arranged more or less perpendicularly 

 on the surface and piercing the dermal layer of small spicules also present here (pi. X, fig. 7). The 

 system of canals is lined b\' a membrane, provided with .spicules of the same size as those of the der- 

 mal membrane, but they are not here so closely packed (pi. X, fig. 5). When the dermal membrane is 

 examined over the edges of the oscular openings down into the canals, all degrees between the more 

 or less close packing of the needles are found, the spicules in the membrane becoming more and 

 more spread. The larger canals are comparatively few, and their chief direction seems to be perpen- 

 dicular through the sponge from the supposed base to the oscular openings of the upper sitrface. 



Spic/tla are oxea, slightly curved in the middle and exceedingly long and evenly tapering from 

 the very middle to the ends; their sizes are exceedingly varying, from 0-14 — 2-o2""". The middle sizes 

 are scarce, and thus the spicules convey the impression of occuring in two groups of sizes. In the 

 smaller ones the bending is not so distinctly in the middle as in the larger, Ijut they are more 

 evenly curved. 



Thus the way in which the spicules occur in the sponge, is in this species about the same as 

 in //. gniilrix, the small oxea partly occuring throughout the tissue, partly forming the spicnlation 

 of the dermal membrane and the membranes of the canals; but contrary to the case in H. goiitrix, 

 the spicnlation of these membranes is here exclusively formed by the smaller oxea without any ad- 

 mixture of the larger ones. 



Topsent (Resultats des Campagn. scient. du Prince de Monaco, Fasc. II, 66, pi. IX, fig- 3) de- 

 scribes a new species, //. pacliasfrelloidcs^ which, as to the form and \'arying in length of the spicules 

 as well as the firm consistency, agrees with the present species, but the largest length of the spicules 

 is stated to be 1-4'"'", and the common length o-93'"". The species of which only one specimen is 

 known, grew incrnsting on a stone. On account of the stated difference in the size of the spicules 

 and the fact, that Topsent does not at all mention that the smaller spicules form an outermost der- 

 mal layer, the present species must be different from pac/iasfrclloidcs , although it is surely nearh' 

 allied to it. 



Locality: Station 90, 64° 45' Lat. N., 29' 06' Long. W., depth 568 fathoms, only one specimen. 



9. Halichondria? difficilis n. sp. 



PI. II, Fig. 7, Pl.X, Fig. 8. 

 Of a very irregular, most frequently tuberous or lobate form. The surface smooth. The outer- 

 most layer forming a dermal layer with closely packed spicules more or less parallel to the surface. The 

 skeleton consists of irregularly spread needles, not closely set. Fibres are not formed. In the skeleton 

 is fo7ir/d incrusted a great n?imber of e.xtraneints bodies. Spicula oxea o-o6 — o-jy'"'". 



