64 PORIFERA. III. 



two groups : the dermal spicules tornota 0-327 o-jj""*/ microsclera chela arcuata of a curious, broad 

 and flat shape, 0-032 o'ojj""". 



Of this species we have one specimen, growing on a shell-fragment of a.Pecten; the specimen 

 grows on both sides of the shell having grown round the edge from one side to the other; the largest 

 extent of the specimen is 15""", and the thickness about 0-5 min . The colour (in spirit) is brownish 

 yellow. The surface is hispid from projecting dermal spicules. The dermal membrane is a thin film, but 

 it is wanting to a great extent on the specimen. Oscula and pores were not observed. 



The skeleton. The dermal skeleton; the dermal spicules form bundles or fibres which stretch 

 from the main skeleton, often from the lower part of this or quite from the base, in an oblique 

 direction up to the surface, and project beyond this, and it is thus chiefly these spicules which cause 

 the hispidity of the surface; outermost the spicules in the bundles are spread out somewhat fan-like. 

 When the sponge is examined from above with a good lens, therefore, the fan-like bundles of dermal 

 spicules are seen. In the membrane chela; are found, but they are very scattered. The main 

 skeleton is of the typical construction, consisting of vertical acanthostyli with their heads fixed on the 

 substratum; the longest of them project beyond the surface and contribute to the hispidity of the 

 sponge. At the base spongin is found, but only to a very slight degree. 



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

 somewhat curved; the head-end is a little swollen, and they taper evenly into a long, fine apex. The 

 spinulation is somewhat strong, the spines on the shaft are compressed and reclined downwards; the 

 spines on the head-swelling are considerably longer, they are not compressed, and radiate straight 

 out; these spines are truncate at the end and sometimes somewhat curved and hook-shaped, the small 

 and intermediate styli are spined in their whole length, the longest styli, on the contrary, have a 

 generally rather short part of the apex smooth. The styli vary much in size, but they are not divided 

 into groups. The length is 0-13 0-45 mm , and the diameter of the head 0-018 0-035""". 2. The dermal 

 spicules are long, straight tornota, they are slightly fusiform; the ends are short pointed, and the 

 points are bounded by straight or concave lines. The fully developed tornota have equal ends, but 

 the developmental stages are monactinal. The length is 0-327 0-53 mm , and the diameter in the middle 

 about 0-005 0-008 mm . b. Microsclera; these are chelae arcuatae; they are of a curious, short and 

 flat shape; the shaft is slightly curved, and is not flattened; the alae are broad and lobe-shaped, and 

 the tooth is rather broad and a little shorter than the alae. The angle between the axis and the tooth, 

 and the curvature of the alae are such, that a transverse section of the chela through alae and tooth 

 would form a transverse ellipse. For the rest the chelae are not rarely of a more or less irregular shape, and 

 some monstrosities are also found. The length of the chelae is 0-032 0-035 """> an ^ the diameter of the 

 shaft about 0-004 """ The chelae occur only in the dermis, but also here only in small numbers. 



Locality: Station 89, 64 45' Lat N., 27 20' Long. W., depth 310 fathoms; the station lies in the 

 Denmark Strait. 



19. H. basispinosa n. sp. 

 PL III, Fig. 5, PL VII, Fig. 6. 



Incrusting ; surface smooth, bearing some small, conical oscular cones with a dense skeleton of 

 dermal spicules in the wall. Spwila: megasclera; the skeletal spicules acanthostyli witli a small head. 



