14 
former specimen there is one osculum that is a little elevated; in 
the latter this elevation is to be seen also, but there are also other 
oscula without wall. So it seems, that a wall is not at alla eonstant 
distinetive character. Both specimens have a pale yellowish colour. 
b. Skeleton. 
The cortieal layer of globulates is rather thick. The other spi- 
cules take their origin in the centrum of the Sponge, here building 
a hard nucleus. The arrangement of the needles and anchors is a. 
radical one. The elements of this skeleton are the following spicules. 
1°. ac? and ae? (f). (Acerate and sub-fusiformi-acerate). As is to be 
seen in the figg. 39, 40 and 41 the acerate spicules are more or 
less sharp pointed; the heads often resemble those of Isops pallida ; 
but it will soon be clear on looking at the figures, that they 
never grow so thick; the length being nearly the same as in J. 
pallida, but the shape is more slender. Frequent. 
2°. tr. ac. f. (fusiformi-acuate). These are not very frequent, always 
longer than the tr. ac. of I. pallida. (Pl. II, fig. 27). 
3°. M. ta. © = 90° (patento-ternate). The shaft (M) and the teeth 
(d.) are thinner than those of /. pallida. .The teeth are sharp- 
pointed, more or less bent. (Pl. II, fig. 42). Frequent. 
4°. M. ta. © < 90° (recurvo-ternate). I have represented two dif- 
erent kinds of the true recurvo-ternate spicules in figg. 45 and 
46 on Plate Il. In comparing them with the analogous spicules 
of I. pallida it will be clear that there is difference enough. The 
shaft is much thicker, rising to the same length. In fig. 46 the 
teeth are very short, rather stout. In both the angle @ is greater 
than in I. pallida. 
5°, M. ta. &< 90°. There is however yet another kind of spieu- 
les, that seems to be characteristic for 2. sphaeroides viz. the 
elegant ones, represented in figg. 43 and 44. I can’t remember 
whether I have seen this eurious spicules in any other Sponge. I 
believe that no representation exists ofit. If Bowerbank had known 
them, he would probably have named them geniculated recurvo- 
ternate. The shaft is long and slender, the teeth not very sharp- 
pointed. They are varying much in length as the figures 43 and. 
