c 2 PORIFERA. III. 



The skeleton. The dermal skeleton ; the dermal spicules form partly bundles, partly they are 

 also seen lying scattered; they lie horizontally or stretch obliquely upwards between the ends of the 

 skeletal styli, without any regularity; they lie horizontally especially just below the dermal membrane, 

 and when the sponge is viewed from above, the spicules are seen lying irregularly below the membrane. 

 The main skeleton consists of vertical, somewhat densely placed acanthostyli, the longest of which 

 project beyond the surface. At the base a slight amount of spongin is found. 



Spicula: a. Mcgasclera. i. The skeletal spicules are straight acanthostyli; the head-end is 

 (inly pronounced to a very slight degree, and the styli are therefore somewhat club-shaped. The 

 spinulation is dense and is both in the small and the large forms continued quite to the point, or the 

 spines are at most a little more dispersed towards the point; the spines are directed downwards; they 

 are distinct but not large. The length of the styli is 0-09— 0-27 mm and the diameter of the head 

 0-015 — 0-024 mm . Though the styli do not vary much in length in all, they are divided however into two 

 groups, the larger ones not going below 0-23"™ and the small not beyond o-i2 mm . 2. The dermal 

 spicules are straight strongyla, they are always a little thicker at one end than at the other, but 

 they are otherwise of the same thickness in the whole length; sometimes they are very slightly poly- 

 tylote. The length is 0-25 — 031 mm and the diameter 0-005 — 0-007 """. b. Microsclera ; these are chelae 

 arcuatae; they are of ordinary shape, the shaft is evenly curved, the tooth elliptical, the ake lobe- 

 shaped and broadly cut below. The length is 0-041— 0-04 7"' m and the diameter of the shaft is 0-003 — 

 0-004 mm . The chelae occur numerously in the dermal membrane, but not, however, forming a layer. 



This species is somewhat related to H. storca, but it is characterised by the styli being more 

 densely spined, and spined to the very point, and the spines are smaller; besides, the styli are divided 

 into two groups; the chelae are of another ] shape, and finally also the dermal spicules show a difference. 



Locality: Station 125, 68° 08' Lat. N., 16 02' Long. W., depth 729 fathoms (bottom temperature 

 -f- o° 8 C); the locality lies North of Iceland. 



9. H. tenuicula n. sp. 



PL VI, Fig. 5. 

 In crusting; surface someivhat hispid. Spicula: mcgasclera ; the skeletal spicules acanthostyli zuith 

 a slightly swollen head and divided info two groups, large, with the apical part slightly spined or smooth, 

 0-286— 0-47""", small, spined in the whole length, 0-12 — o-i$""" ; dermal spicules strongyla 0-238— 0-3 1'"'"; 

 microsclera chelce arcuatm 0-032 — 0-037'"'". 



Of this species we have four specimens growing as thin incrustations on a Hamacantha impli- 

 cans, on a Brachiopod-shell, on a tube of Placostcgus tridentatus and finally on a stone, bearing a 

 specimen of Petrosia crassa; the largest specimen grows on the Brachiopod-shell, and it reaches the 

 same extent as this, viz. 25 mm , but for the rest it grows on both sides of the shell which it thus quite 

 covers. The sponge is very thin, scarcely reaching more than 0-25""" in thickness; this is, as will be 

 seen below, less than the length of the largest styli, which consequently project beyond the surface. 

 The colour (in spirit) is slightly yellowish. The surface is distinctly hispid on account of the projecting 

 of the longest styli. The dermal membrane may be traced as a thin film, supported by the dermal 

 spicules. Pores and oscula were not to be seen. 



