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 anchor-teeth. For these I establish the subgenus 

 Prionema. Of the fifty species previously known there are, I beUeve, only two, 

 //. poculum F. E. Schulze ' and H. validum F. E. Schulze,^ 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. rohustum F. E. Schulze, H. globiferum F. E. Schulze, 

 and H. pedunculatum 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. 



' F. E. Schulze. Rept. V03'. Challenger, 1SS7, 21, p. 208. (This serration is not shown in the 

 figure of a macramphidisc of this species. Loc. cil., plate 33, fig. 4). 



= F. E. Schulze. Hexactinellida. Ergeb. Deutsch. tiefsee-exped., 1904, 4, p. 82, taf. 34, fig. 8. 



