_, PORIFERA. III. 



74 



25. H. bractea n. sp. 

 PL, VIII, Fig. 3. 



Incrusting; surface hispid. Spicula: megasclera; the skeletal spicules acanthostyli, divided into two 

 groups, large, with a small head, only spined in the lower part, 0-28— o-j6 """, small, without head, entirely 

 spined. 0-12—0-15"""; the dermal spicules tylota 0-27—0-50"""; microsclera chelce arcuate 0-026' — 0-034""". 



Of this species we have only a very small specimen, and the description will therefore in some 

 respects not be quite satisfactory. The specimen grows on a Brachiopod-shell together with a specimen 

 of Hymenancora duplicata 11. g. et sp. (to be described hereafter), and a small specimen of Melonanchora 

 emphysema. It forms a very small, almost circular incrustation, scarcely two millimeters in diameter 

 and very thin; it bears about in the middle a low, cylindrical papilla. The colour (in spirit) is greyish, 

 and the sponge is somewhat transparent. The surface is in the present state hispid from projecting 

 skeletal styli. About the dermal membrane I can say nothing, and also nothing about pores and oscula ; 

 probably the papilla mentioned is an osculum, but I could not observe it. 



The skeleton. The dermal skeleton seems to consist of scattered bundles of dermal spicules, 

 and it is, so far as I could observe, relatively weakly developed. The main skeleton is constructed in 

 the ordinary way and consists of vertical acanthostyli with their heads on the substratum, and it is 

 somewhat dense; the longest of the acanthostyli project beyond the surface, and it seems to be so 

 also in the undamaged sponge. 



Spicula: a. Megasclera. 1. The skeletal spicules are acanthostyli which are divided into 

 two groups, large and small. The large acanthostyli are straight, they have a small head-swelling 

 and taper evenly into a long apex which is a little more abruptly pointed outermost; they are spined 

 only on the basal part, at most on the half part; the spines are of medium size, largest below; they 

 are placed most densely on the head-swelling, but more dispersed outwards. The small styli have no 

 head-swelling; the base is the thickest part and from here they taper evenly to the point, thus as- 

 suming a club-like shape; these styli are spined in their whole length, the spines at the base radiate 

 straight out, those on the shaft are reclined. The length of the large styli is 0-28— 0-36 mm , and the 

 diameter of the head is about o-02 n,ra ; the length of the small styli is 0-12— o-i5 mm with a diameter at 

 the base of ooi4 mm . 2. The dermal spicules are straight and somewhat slender tylota, the end- 

 swellings are distinct but not large; the length varies rather considerably, from 0-27 — 0'50 mm , and the 

 diameter of the shaft is 0-004 — o-oo7 mm . b. Microsclera ; these are chelte arcuatse, they have a curved 

 shaft, elliptical teeth and lobe-shaped but somewhat narrow alae. The length of the chela is 0-028 — 

 0-034 n,m , and the diameter of the shaft 0-004— 0-005 mm . The chelje seem to occur through the whole 

 tissue, but are seen especially at the surface. 



Locality: Station 89, The Denmark Strait, 64 45' Lat. N., 27 20' Long. W., depth 310 fathoms. 



26. H. laevistylus n. sp. 

 PI. VIII, Fig. 4. 

 Incrusting. Spicula: megasclera : the skeletal spicules acanthostyli with a very small head, only 

 spined 011 and just at I In- head, for the rest smooth, very uniform in size. 0-44 — 0-48""" : the dermal 

 spicules tylota varying to strongyla, o-2j — o-j4""" ; microsclera cliche arcuata- 0-045 — 0-052""". 



