IIO PORIFERA. III. 



Spicula: a. Megasclera. i. The skeletal spicules are acanthostyli which are not divided 

 into two groups, in so far as intermediate forms occur, but as these are somewhat rare, the styli give 

 the impression of falling into two groups; the large styli are straight or very slightly curved, they 

 have a roundish head with moderately sized spines, the shaft has small spines which become quite 

 gritty outwards; the small styli are generally straight, the head is less pronounced than in the large, 

 the spines are larger and often distinctly reclined. The length of the styli is in all 0-107— 0-31 mm and 

 the diameter at the head 0-014— o - 02i 1I,m . 2. The dermal spicules are long, straight, or somewhat, 

 often irregularly, curved tornota; they are thickest in the middle and thus more or less fusiform; they 

 show a curious feature, the end-parts being generally, but not always, somewhat roughened or micro- 

 spined. The length is 032— 0*47 ram and the diameter in the middle 0-004 — 0-007 mm . Microsclcra are 

 not present 



Locality: Station 81, 6i°44' Lat. N., 27° oo' Long.W., depth 485 fathoms; station 89, 64 45' Lat. N., 

 27° 20' Long. W., depth 310 fathoms; East of the Faroe Islands, depth 160 fathoms. The localities lie 

 in the Denmark Strait, South-west of Iceland and at the Faroe Islands. 



51. H. mucronella n. sp. 

 PL HI, Fig. 19, PL XI, Fig. 3. 



Incrusting, but of somewhat massive appearance; surface hispid. The dermal skeleton strongly 

 developed, the main skeleton weak. Spicula: megasclera ; the skeletal spicules acanthostyli divided into 

 two groups, large with a very small head, only spined below, o-jo — 0'6j""", small, with a more distinct 

 head, and entirely spined, o-ij — 0-178""" ; the dermal spicules tornota with one end with a mucro, o-j8 — 

 o 4 5p6""". No microsclcra. 



Of this species we have only one specimen which grows on a fragment of a Sipho; the sponge 

 is of a somewhat massive shape as it does not incrust the shell-fragment but is only fixed on it and 

 is for the rest somewhat filled with bottom material; it thus shows a growth similar to that in H.grandis, 

 though it is much less filled with foreign particles. On account of large cavities in the sponge the 

 consistency is somewhat bladder-like. The specimen has an extent of 17 n,m and a height of about 

 gmm The colour (in spirit) is dark greyish brown. The surface is strongly and densely hispid from 

 projecting dermal spicules. Oscula and pores were not observed. 



The skeleton. The dermal skeleton; the skeleton formed of the dermal spicules is strongly 

 developed and occupies the greatest part of the sponge; it consists of fibres running everywhere but 

 chiefly in the direction from the base, or else from some part of the main skeleton, towards the 

 surface, the fibres may thus attain a relatively great length; in the dermal membrane the spicules 

 form penicillately spread bundles, the spicules of which pierce the membrane; seen from above the 

 spicules in the bundles appear almost stellately arranged; in places where the membrane stretches 

 over the large cavities, fibres pass horizontally just below it, and the bundles seem here to originate 

 from these fibres. The sponge-body has, as said, many large cavities and the fibres are found 

 therefore in the parts of the tissue separating these cavities. The main skeleton is not much 

 developed; it consists of acanthostyli based with their heads partly on the shell at the base of the 



