HYALONEMA. 
151 
propose a new arrangement, based on the results of my examination of the 
twenty-four Pacific species. 
These results have led me to think that certain characters of the amphi- 
discs could be utilised for this purpose. It is true that the numerous very differ- 
ent forms of these spicules are to a great extent connected by transitions ; there 
are, however, in spite of this, some amphidisc-forms not so connected. 
The anchor-teeth of the amphidiscs of most of the Pacific Hexactinellida 
have smooth margins. In five of them, however, there occurs a particular kind 
of amphidiscs with serrated anclior-teeth. For these I establish the subgenus 
Prionema. Of the fifty species previously known there are, I believe, only two, 
II. poculum F. E. Schulze 1 and H. validum F. E. Schulze , 2 in which amphidiscs 
with serrated teeth have been noticed and described. I think it highly probable, 
however, that such amphidiscs occur in others also, as for instance in H. lusita- 
nicum Bocage, and H. cupressiferum F. E. Schulze, where they have not been 
mentioned either because they were overlooked — they are generally small and 
clearly visible only with high powers — or because the authors who studied these 
sponges did not consider them of importance. 
Most of the species of Hyalonema examined by me in which the anchor- 
teeth of all the amphidisc forms are smooth-margined, generally have hyper- 
bolic, semispherical, or bell-shaped anchors and measure from about a quarter 
to a third of the whole spicule in length. In some of them, however, the amphi- 
disc-anchors are of other relative dimensions and often also of another shape. 
In five of the Pacific species examined, one of which had been previously de- 
scribed, the anchors of a certain kind of amphidiscs are more or less semi- 
spherical and about half as long as the whole spicule, so that the two anchors 
of the same spicule nearly or quite meet in the middle. For these species I 
establish the subgenus Oonema. Of the species previously described there are, 
besides the one in the A. Agassiz Pacific collection above referred to, four ( H . 
tenerum F. E. Schulze, H. robuslum F. E. Schulze, H. globiferum F. E. Schulze, 
and II. pedunculcitum Wilson) which can certainly, and one ( H . ovuliferum 
F. E. Schulze) which can perhaps, be assigned to this subgenus. 
In two of the Pacific species examined by me, one of which had been previ- 
ously described, the anchors of the largest amphidiscs are small and relatively 
very short and broad. For these species I establish the subgenus Phialonema. 
1 F. E. Schulze. Rept. Voy. Challenger, 1887, 21 , p. 208. (This serration is not shown in the 
figure of a macramphidisc of this species. Loc. cit., plate 33 , fig. 4). 
2 F. E. Schulze. Hexactinellida. Ergeb. Deutsch. tiefsee-exped., 1904, 4 , p. 82, taf. 34, fig. 8. 
