PORIFKRA. II. 



23 



point they grow fewer, and at the very end they are quite few, in quite undamaged appendices per- 

 haps only a single one. In the covering layer of tissue an abundance of microsclera is found; along 

 the fibre, at least to the middle of it, the large chela is arranged in beautiful rosettes, and between 

 these rosettes the little chela is found in dense crowdings (PI. IX, fig. 4), but forming no rosettes. 

 The sponge is throughout highly intervowen with sand and small silicious particles. 



Spicula: a. Megasclera are very slender, straight styli; they taper evenly, but not much, towards 

 the pointed end, the point itself is rather short. The length varies from c/33— o-45 mn ', and the thick- 

 ness from 0-004 — o-oo57 mm . Finer developmental forms are found, but only singly, b. Microsclera are 

 two forms of isochelse palmatse. 1. The large chelse are of a very regular and beautiful form. The 

 shaft is straight, the free middle part a little curved inward. The alse reach so far down the shaft, 

 that the free middle part is only about one fourth of the length, and their sides are somewhat refolded. 

 The tooth is of the same length as the alse and only a little narrower. Its edge is curved a little 

 inward. Tuberculum is longish, broadest below. When the tooth is seen from the inside the axis may 

 be seen some way down it. Not rarely a slight twisting of the chela is observed. The length is 0-064 

 — 0-075™"', anc * the breadth is o-o2i m,n . A few developmental forms of this chela were seen. 2. The 

 small chela has a quite slightly curved shaft, the end parts are so long, that the free middle part 

 of the shaft is quite short. The lateral edges of the alas form a far more curved line than in the 

 large chela, and their lower edge is straight. The sides of the alte are somewhat refolded. The tooth 

 is of the same breadth as the alas, and the tuberculum is a little longish. The alse and the tooth 

 form a very small angle with each other. The length is 0-021 — o-o25 mm , quite singly specimens were 

 seen of a length of 0035""". The breadth is o-oo8 mm . The occurrence of the chelse is quite singular; 

 to be sure they are to be found throughout the tissue, but especially at the surface. The large chela 

 occurs as rosettes which seem to be attached to the fibres, especially at the dermal membrane, but 

 not in this membrane itself. It is seen arranged in rosettes in the layer of tissue on the projecting 

 ends of the fibres. Also the small chelse are especially seen at the surface; they do not form rosettes 

 but occur in groups or dense crowdings. Both kinds of chelae occur also, as before mentioned, in the 

 flagelliform appendices. The occurrence of the large chela in typical rosettes is rather interesting, as 

 this fact is otherwise not known in the isochelse, but has only been observed in anisochelse. Carter 

 meutions rosettes of chelae in Mycale titubans, and thinks here to have found isochelse in rosettes; as 

 will be mentioned hereafter, under the species in question, its chelae, however, are anisochelse. 



This species shows itself to be related to the preceding one; the megasclera are of the same 

 form, and also the large chela is of the same structure. Also the skeletal structure seems to be the 

 same as well with regard to the arrangement as to the fact that spongin is wanting. On the other 

 hand the small chela is of a different structure, and no kind of sigmata is found. 



Locality: Forsblads fjord, East Greenland, depth 50—90 fathoms (the Amdrup-Expedition 1900). 

 Only one specimen. 



Mycale Gray. 



The habitus may pass through the whole series of forms from thinner or thicker incrustations 

 through massive forms to erect , often lobate, or finally branched or more or less irregularly leaf- or cup-shaped 



