PORIFERA. III. 



consists of vertical acanthostyli with their heads based on the substratum; the longest of them reach 

 the dermal membrane, but do not pierce it. Just at the base of the sponge there is, I believe, a 

 slight amount of spongin, but I was not able to see it with absolute certainty. 



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

 they have a slightly swollen head and taper evenly into a long apex which outermost is a little more 

 abruptly pointed. The spines on the head are large, they are not pointed but truncate and not rarely 

 somewhat hook-shaped. The spines on the shaft are somewhat dense and continue out to the point, 

 but they are more scattered in the outermost part; the spines are reclined and compressed, so that 

 they get the shape of a tooth of a saw. The styli vary greatly in size, and as intermediate forms 

 are very scarce they are divided into two groups, which are, however, not quite sharply limited. 

 The length lies in all between 0-15 and 0-429"', and the diameter of the head is 0-025 0-040""". When 

 the single intermediate sizes are not considered the two sizes will be about 0-15 o-ig"'" 1 and 0-30 

 0-429'""'. 2. The dermal spicules are slender, straight, or more rarely slightly curved, polytylote 

 strongyla, the ends are generally slightly swollen, so that the spicules approach to subtylota; one end 

 is as a rule a little thicker than the other, and the thinner end has the largest swelling; the swellings 

 are the more distinct the thinner the spicule is, in the thickest strongyla they are very slight or quite 

 wanting. The strongyla vary somewhat in size, the length is between 0-31 and 0-41 7 mm , and the 

 diameter is 0-005 o-oo8 mm . b. Microsclera are chelae arcuatse; they have a curved shaft and the 

 ends are somewhat recurved; the tooth is lanceolate, with a long tuberculum, and the alae are of the 

 same length as the tooth; the shaft is somewhat flat, and nearly always slightly dilated in the middle. 

 The chela is rather large, and the size is somewhat constant, the length is 0-052 0-064""", and the 

 diameter of the shaft varies from about 0-005 o-on mm m relation to the chela being seen in front or 

 in side view, and to the dilatation in the middle of the shaft being larger or smaller. Single develop- 

 mental stages were seen. The chelae occur, as said, in enormous numbers and densely crowded in 

 the dermal membrane, and they do not seem to occur otherwise in the body of the sponge. 



Locality: Station 9, 64 18' Lat N., 27 oo' Long. W., depth 295 fathoms. Two specimens. The 

 locality lies in the Denmark Strait. 



8. H. splenium n. sp. 

 PI. VI, Fig. 4. 



Incrusting; surface hispid. Spicula: mcgasclera; the skeletal spicules densely and entirely 

 spine d acanthostyli ^oith a very slightly marked head, divided into fwo groups, large 0-23 0-27""", small 

 0-09 0-12"""; the dermal spicules strongyla 0-25 0-31""" ; microsclera chela arcuatce 0-041 0-047""". 



This species grows as rather extended incrustations on a somewhat large stone; it has a 

 greatest extent of about 16""", the thickness is small, below 0-5""". The colour (in spirit) is whitish 

 grey. The surface is dispersedly hispid from projecting skeletal styles, and it seems to be so also when 

 the dermal membrane is undamaged. The dermal membrane is a thin film, resting on the skeleton 

 below. Here and there larger and smaller openings for the canal system were observed, partly placed 

 in groups; they are probably both pores and oscula, 



7* 



