6 2 PORIFERA. III. 



canal system. At the base of the sponge there is found a somewhat rich amount of spongin in 

 which the heads of the styli are imbedded. 



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

 generally slightlv curved; they have no head-swelling marked off or this is only weakly pronounced, 

 and thev taper evenly into a long, rather fine apex, and accordingly they are of a more or less club- 

 like shape. The size varies to a high degree, and in relation to the size the spinulation also varies, 

 but separate groups of size do not exist. The smaller the styli are the relatively stronger they are 

 spiued, and the spines are on the small styli continued out to the very point; the longer the styli, 

 the longer a part of the apex remains smooth; in the large styli also the close-standing, some- 

 what large spines on the head-end are relatively smaller than in the small styli, and the spines placed 

 on the shaft are very small. The spines are in this species only slightly, or not at all reclined. The 

 length varies from o - o8o — 0*53 mm , and the diameter at the head is about o-oi 1—0-031 mm . 2. The dermal 

 spicules are thin tornota; they are straight, of the same thickness in the whole length or quite 

 slightly thicker in the middle; the points are typical tornote points, short and bounded by straight 

 lines, and they are very sharply pointed. The fully developed tornota have the two points uniform 

 or nearly uniform. The length is 0-178 — o-22 mm , and the diameter about 0-0028— 0-0040 mm . b. Micro- 

 sclera are chelae arcuatae; they have an evenly curved shaft, an elliptical tooth with a long 

 tuberculum, and alse of the same length as the tooth. The size varies very much, the length from 

 o-02i— 0-054 mm an d the diameter of the shaft is in relation to the size 0-002 — 0-007""". Some single 

 developmental stages were seen. The ehelse occur numerously in the dermal membrane, and are also 

 seen singly lower down in the sponge. 



Locality: Station 4, 64 07' Lat. N., n° 12' Long. W., depth 237 fathoms; station 6, 63 43' Lat. N., 

 14 34' Long. W. , depth 90 fathoms; station 9, 64 18' Lat. N., 27 00' Long. W., depth 295 fathoms; 

 station 16, 65° 43' Lat. N., 26 58' Long. W., depth 250 fathoms; station 27, 64 54' Lat. N., 55 io'Long.W., 

 depth 393 fathoms; station 28, 65" 14' Lat. N., 55 42' Long. W., depth 420 fathoms; station 85, 63 21' 

 Lat. N., 25 21' Long. W., depth 170 fathoms; further, it has been taken at 63° 05' Lat. N., 22 23' 

 Long. W., depth 115 fathoms and 63 21' Lat. N., 16 22' Long. W., depth 296 fathoms. The localities lie 

 in the Davis Strait, the Denmark Strait, South of Iceland and between Iceland and the Faroe Islands. 



17. H. clavigera n. sp. 

 PI. Ill, Fig. 8 b, PL VII, Fig. 4. 



I nc rusting, thin ; surface hispid. Spicula: megasclera ; the skeletal spicules club-shaped acantho- 

 styli, divided into two groups, both entirely spined, large 0-25— 0-298""", small 0-093— 0-12""" ; ^ lc dermal 

 spicules tornota o-/6 — o-iyS"""; microsclcra chetcc arcuala- 0-041 — 0-032""". 



This species grows incrusting on a stone, which bears several other small sponges, and it 

 grows epiite close to a specimen of //. Bowerbanki n. sp. to be described hereafter; it has a greatest 

 extent of 12"'"', and it is exceedingly thin and delicate. It is of a whitish colour (in spirit). The 

 surface is very hispid on account of the erect styli being protruding. The dermal membrane is 

 imperceptible and not separable, but it appears to be a very delicate membrane, richly provided, 



