PORIFERA. III. 



"9 



no horizontal spicules in the membrane itself. The main skeleton is constructed as usual of acantho- 

 styli with their heads placed on the shell, the longest of them reach to the dermal membrane and 

 project beyond it. At the base there is a small amount of spongin. 



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

 groups, large and small; the large styli are generally slightly curved, they are a little thickened at 

 the base, but there is no head-swelling, they taper only slightly outwards and the point is somewhat 

 short; the styli are spined in almost the whole length, only a small part of the apex being smooth or 

 nearly smooth; at the base the spines are of medium size and numerous, outwards they are small, 

 nearly gritty, and more scattered. The small styli are mainly of the same shape as the large, they 

 are straight or slightly curved and have likewise no head-swelling, but they are spined in the whole 

 length. The length of the large styli is 0-29— 0-41 mm with a thickness at the base of 0-016— cro2 1 n,ra , 

 the small styli are cru— o-i3 mm long with a diameter at the base of o-on— ooi4 mm . 2. The dermal 

 spicules are tylota with the swollen ends pointed like toruotes; the shaft is slender and generally 

 straight, sometimes it is very slightly polytylote; the ends are distinctly but not much swollen, and 

 they are pointed in such a way that the spicule might be termed a tornote were it not for the 

 swellings. The length is o-i6— o-22 mm , and the diameter of the shaft is 0-0028 — o-oo4 mm . b. Microsclera 

 are of two forms, ancorae spatuliferse and sigmata. 1. The ancorae resemble those in interjecta, but 

 they are a little less curved or the curve is distinctly localized in the middle of the shaft; they have 

 three elliptical teeth at each end, the alse are not large but distinct and always present. This ancora 

 is thus evidently related to that in interjecta, but it is less chel-like. The length is o - 022— 0-042 m:n 

 and the thickness of the shaft is 0002— 0-004 mm ; the large ancorae are by far the most numerous while 

 the smaller are seen only rarely. 2. The sigmata are of ordinary shape and they are contorted, 

 generally a quarter of a turn. The length is 0-035— °'°4 5 mm an< ^ tne thickness about o-oo28 mm . The 

 sigmata occur in the tissue of the sponge but not in the dermal membrane, the ancorae occur also in 

 the tissue but especially in the dermal membrane and here rather numerously. 



This and the preceding species are nearly related, but they are characteristically different in 

 the shape of the dermal spicules, the size of the sigmata and also in the shape of the ancorae. 



Locality: South of Iceland, 63 21' Lat. N., 16° 22' Long. W., depth 296 fathoms (The Fishery 

 investigation steamer "Thor"). 



3. H. duplicata n. sp. 

 PI. XI, Fig. 6. 



Incrusting ; surface hispid? Spicula: megasclera; the skeletal spicules acanthostyli with a small 

 but distinct head-sivelling, the largest only spined at the base, the shorter they are the longer a part is 

 spined, and the shortest are spined in the whole length, 0-12 — o-^y" 1 " 1 , not divided into two groups; the 

 dermal spicules tornota 0-238— 0-31""" ; microsclera ancora: spatulifera of two forms, large, with j — 6 

 teeth, 0-062—0-071""". small, with S — // teeth, 0-032 — 0-038""". 



This interesting species grows as thin incrustations on Brachiopod-shells; its greatest extent is 

 11™ and the thickness is about o-25 mm . The colour (in spirit) is whitish or light yellowish. The 

 surface is in the present condition of the sponge strongly hispid from projecting acanthostyli, but it 



