PORIFERA. III. 



83 



characteristic differences lie in the spicules, the acanthostvli have no pronounced head, they are more 

 slender and are divided into two groups; the dermal spicules are not polytylote, and the chelae have 

 a diffreent shape and are smaller. 



Locality: Station 85, 63 21' Lat. N., 25 21' Long. W., depth 170 fathoms; the station lies in the 

 Denmark Strait. 



32. H. crux O. Schmidt. 

 PL III, Fig. 11, PL VIII, Fig. 10. 



1875. Desmacidon crux O. Schmidt, Jahresber. der Coiiim. zur wissensch. Unters. der deutsche Meere 



in Kiel fiir 1872-73, 1875, 118, Taf. I, Fig. 10-11. 

 1903. Hymedesmia crux, Thiele, Arch, fiir Naturgesch. Jahrg. 1903, I, 392, Taf. XXI, Fig. 26 a— d. 



Incrusting; surface smooth, generally with lour, oscula-b earing, conical warts with a skeleton of 

 dermal spicules in the wall. Spicula: megasclera ; the skeletal spicules acanthostyli with a well-marked 

 head, spined in the whole length, o-i2—o-j8 mm , not divided into two groups; the dermal spicules sub- 

 tornota varying through tornostrongyla to strougyla, they are polytylote, o-2jr—o-j8 mm ; microsc/era chela 

 arcuata with a spined shaft, o-oji — crojj""". 



Of this remarkable and very interesting species we have about ten specimens; they form small 

 or more extended incrustations on stones and worm-tubes, one grows on a Pecten-shell; the greatest 

 extent it reaches is about 35 ram , and the thickness lies between 0-5 and i mm . The colour (in spirit) is 

 yellowish red, brownish red or reddish, the sponge may thus vary somewhat in colour, but it always tends 

 towards reddish. Schmidt 1. c. says about the colour "braungelb", and one of the Ingolf specimens 

 is stated to have been yellow in the fresh state. The surface is smooth in so far as there are no 

 projecting spicules, but it is often wrinkled and folded to a higher or lower degree; this latter fact is 

 probably only due to contraction. The dermal membrane is rather thick and solid, and it is easily 

 separable; it is very densely charged with chelae, more densely than in any other species of Hyme- 

 desmia ; the chelae form a dense and solid layer. Oscula and pores: oscula are found as low, conical 

 warts scattered on the surface; they have an opening or a depression in the summit, and around this 

 the surface may be a little stellately rugose. In my specimens the warts are, as said, quite low, 

 sometimes scarcely elevated above the surface; Schmidt says on the other hand "Oscula auf unregel- 

 massigen Papillen"; according to this it would seem, that the oscular cones may sometimes be higher, 

 if it is not irregular folds of the surface, that Schmidt has mistaken for cones. In some specimens 

 the warts are easily discernible, in others they are more or less indistinct, and they may be quite 

 absent. Pores I have not seen and cannot say whether they are scattered or perhaps collected in 

 definite areas; sometimes some larger, dendritically branched canals may be seen through the dermal 

 membrane. 



The skeleton. The dermal skeleton ; the most protective skeleton of the dermal membrane is 

 formed by the mentioned dense layer of chelae; the dermal spicules form bundles stretching from the 

 main skeleton, often almost from the base, up to the dermal membrane; in the membrane itself no 

 dermal spicules are found. Around the oscula the dermal spicules form a special oscular skeleton, the 



