PORIFERA. III. 



however, with chelae. Oscula and pores were not seen, but the sponge is perforated by close-standing, 

 vertical canals which shine through the dermal membrane and are seen on the surface as dark, round 

 points; it would seem that the oscula are simple openings in the membrane, and the pores lie 

 several together over the openings of the incurrent canals. 



The skeleton. The dermal skeleton consists of dermal spicules stretching from the skeleton 

 below and out to the dermal membrane; it is very weakly developed and seems only to consist of 

 single spicules, not forming bundles, and the spicules are not numerous. The main skeleten is formed 

 in the ordinary way of erect acanthostyli with the head-ends based on the substratum, the longer of 

 them protrude far beyond the surface; a very faint amount of spongin is present at the base. 



Spicula: a. Megasclcra. i. The skeletal spicules are acanthostyli, and they are rather 

 characteristic; though the basal end is the thickest part of the spicule there is however no head- 

 swelling developed at all; from the basal end the spicule becomes only slightly thinner outwards, 

 and the point is somewhat short; the spicule thus has a somewhat club-like shape; they are generally 

 slightly curved. The styli are divided into two well defined groups, large and small. The large styli 

 have a somewhat slight spinulation, only at the base there are some stronger, but however rather 

 small spines, they are blunt and generally curved somewhat upwards towards the apex of the style; 

 on the other part of the style the spines are small, but they are present to or near to the point, and 

 they are reclined. The small styli have quite the same shape as the large, only they are generally 

 not curved and the spines are relatively larger. The length of the large styli is 0-25 cragS" 1171 , with 

 a thickness at the base of 0-021 mm , and of the small styli 0-095 0-12 mm with a thickness of about 

 0-013 mm. as is seen the two groups are fairly distinct in size, and the variation in each group is only 

 slight. 2. The dermal spicules are tornota; they are straight, rather thin and of equal thickness 

 in the whole length; the points are short and sharp; the length is 0-16 0-178""", and the diameter 

 o-oo2 ram . b. Microsclera are chela? arcuatse; they have an evenly curved shaft, the alse are lobe- 

 shaped with the lower edge broad and straightly cut off, and the tooth is elliptical. The length is 

 0-041 0-052 mm and the thickness of the shaft 0-005 0-007 mm . The chelae are abundantly present in 

 the dermal membrane. 



This species is nearly related to H. perforata, but it is distinguished by several characters; the 

 main skeleton is less dense, the acanthostyli not being so densely crowded, the two distinct groups of 

 acanthostyli are not present in perforata, and the acanthostyli are in the present species much less 

 spined and in their whole length, while in perforata they are more strongly spined, but with the 

 apical part smooth; also in the shape of the tornota and the chelae there are small differences, and 

 finally the sizes of the spicules are different. 



Locality: The Denmark Strait, 65 50' Lat. N., 26 53' Long. W., depth 208 fathoms (The Fishery 

 investigation steamer "Thor"). 



18. H. platychela n. sp. 

 PI. VII, Fig. 5. 



Incrusting; surface hispid. Spicula: megasclcra; the skeletal spicules acanthostyli with a small 

 head, somewhat strongly spitted in the whole or nearly the whole length, o-/j 0-45""", not divided into 



