PORIFERA. III. 



The skeleton. The dermal skeleton. Besides the chelse filling the dermal membrane, this is 

 supported by bundles of dermal spicules, which stretch upwards from the main skeleton; further some 

 scattered spicules are present in the membrane. The main skeleton consists as usual of vertical 

 acanthostyli with their head-ends fixed on the substratum. The longest of the styli reach to the 

 dermal membrane, but without projecting through it. A slight amount of spongin seems to be found 

 just at the substratum, but it is at all events difficult to observe. 



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

 slightly and evenly curved; they have generally a somewhat distinct head-swelling, and they taper 

 from the head into a long apex, which may be more shortly pointed outermost. The spinulation is 

 dense in the lower part of the style, but it is more dispersed outwards; in the longer spicules an 

 apical part is smooth, while the shorter ones are spined to the point The spines on the shaft are 

 reclined, on the head they are placed more densely and are longer, radiating straight out and generally 

 truncate. The 'acanthostyli vary much in size, but they are not divided into two groups. The length 

 is 0-077 O'2i4 mm , and the diameter at the base is o'on 0-028"'. In some specimens the styli did not 

 reach beyond O'i78 mm . 2. The dermal spicules are strongyla varying to subtylota; they are straight, 

 sometimes a little polytylote but only to a slight degree. The ends may be simply rounded but they 

 are most frequently slightly swollen; they are not equal, one being a little thinner than the other, 

 and this thinner end shows the most distinct swelling. The length varies in all between 0-15 and 

 o - 238 mm ; in the single specimens the variation is only slight. The thickness is about 0-002 0-004 mm . 

 b. Microsclera; these are chelse arcuatse; they are rather small, they have an evenly, generally 

 somewhat strongly curved shaft, but with regard to this curvature there may be some little variation; 

 the tooth is lancet-like, and the alse of the same length as the tooth. The teeth have such a 

 direction, that they lie in a straight line drawn from one end of the chela to the other. The 

 length of the chelae is 0-021 o-O25 mm , and the diameter of the shaft 0-002 0-028 mm . The chela; 

 occur in great numbers in the dermal membrane, sometimes somewhat scattered and sometimes 

 quite close-lying; this difference is probably due to the greater or less contraction of the 

 membrane. 



As I find no characters separating this species from H. baculifera Tops., I have referred it to 

 the latter; especially the figures cited appear to me very like the spicules in the present species. 



Locality: Station i, 62 30' Lat. N., 8 2 1' Long. W., depth 132 fathoms; station 9, 64 18' Lat. N., 

 27 oo' Long. W., depth 295 fathoms; station 54, 63 08' Lat. N. , 15 40' Long. W., depth 691 fathoms; 

 station 86, 65 03' Lat. N., 23 47' Long. W., depth 76 fathoms; station 94, 64 56' Lat. N., 36 19' Long. W., 

 depth 204 fathoms; station 98, 65 38' Lat. N., 26 27' Long. W., depth 138 fathoms; further it has been 

 taken at 63 12' Lat. N., 20 06' Long. W., depth 270 fathoms (The fishery investigation steamer "Thor"), 

 and East of the Faroe Islands, depths 220 and 250 fathoms (Ad. Jensen, the cruise of "M. Sars" 1902); 

 in all about 14 specimens. The station on which most specimens were collected was station 85, the 

 sponge here growing on tubes of Placostegus. The enumerated localities are situated in the Denmark 

 Strait, South of Iceland and East of the Faroe Islands. 



Geogr. distr. Topsent records the species from the Mediterranean North of Algiers, and at 

 38 35' 30" Lat. N., 28 05' 45" Long. W., depth about 660 fathoms. 



