PORIFERA. III. g t 



of the irregularity of the substratum on which the sponge grows, the styli may show some irregularity 

 with regard to direction. On the same account there may be great difference with regard to the 

 relation of the main and the dermal skeleton to one another; when the sponge grows directly on the 

 shell or the stone the construction is the common one, and the larger styli reach to the surface; but 

 when the substratum is irregular, and the sponge therefore grows thicker in places, the skeleton 

 formed of the dermal spicules increases in extent and forms fibres going up to the surface; this 

 skeleton forms in such places the greatest part of the whole skeleton of the sponge, the main skeleton 

 always remaining formed of the vertical styli attached to the substratum. A small amount of spongiu 

 seems to be found at the base, but at all events only to a very slight degree. 



Spicula: a. Megasclera. i. The skeletal spicules are acanthostyli ; they are straight or 

 generally somewhat curved near the base; the curvature is present especially in the longer styli. The 

 styli have a distinctly marked, globular head, and they taper into a long, fine apex. As commonly 

 the small styli are entirely spined, the longer the styli are the more dispersed are the spines, and the 

 longer a part of the apex is smooth. The spines on the head are densely placed, and they are the 

 largest; on the shaft they are compressed and reclined. The styli vary much in size; even if the 

 intermediate forms are rare, there are however not two separate groups of size. The length is 0-12 

 0-50, and the diameter of the head is 0-021 o'O3O ram . 2. The dermal spicules are of a very- 

 characteristic shape and must be termed styli; they are straight, one end is rounded, the other tapers 

 evenly into a long apex which is more abruptly pointed outermost; the spicules are thickest in the 

 middle, and they are polytylote, showing on the middle part a series of swellings; near the rounded 

 end there is a somewhat sudden narrowing which forms a handle-like part. The length of the 

 dermal spicules is 0-298 o'39 mm and the diameter in the middle 0-006 o-oio mm . b. Microsclera; these 

 are chelae arcuatae; they are of ordinary shape with an evenly curved shaft, an elliptical tooth and 

 alse of the same length as the tooth. The length of the chelae is 0-040 o-O5O mm ; the shaft is some- 

 what flattened, its diameter is in front and side view about 0-004 0-008 mm respectively. The chelae are 

 found, as mentioned, in the dermal membrane forming a dense layer. 



Locality: Station 10, 64 24' Lat. N., 28 50' Long. W., depth 788 fathoms; station 16, 65 43' Lat N., 

 26 58' Long. W., depth 250 fathoms; station 85, 63 2 1' Lat. N., 25 21' Long. W., depth 170 fathoms; 

 further it has been taken in the Denmark Strait at about 65 Lat. N., depth unknown, at 62 29' Lat. N., 

 5 17' Long.W., depth 160 fathoms and South-west of Suder0, depth 180 fathoms (Ad. Jensen, the cruise 

 of "M. Sars" 1902). About ten specimens in all. The localities lie in the Denmark Strait and at the 

 Faroe Islands. 



31. H. proxima n. sp. 

 Tab. VIII, Fig. 9. 



Incrusting ; surface hispid. Spicula: megasclera; the skeletal spicules acanthostyli without a real 

 head, divided into two groups, large, only spined below, 0-4 j 0-62""", small, entirely spined, 0-14 

 o-i8 mm ; the dermal spicules styli 0-28 o-jj mm ; microsclera ckelce arcuata, 0-023 o-ojj""*. 



Of this species we have two specimens growing as thin, but rather extended incrustations on 

 tubes of Placostegus tridrntahis. The greatest extent of the sponge, which, of course, follows the 



The Ingolf-Expeditinn. VI. 3 II 



