HYALONEMA (OONEMA) SEQUOTA. 355 
guish four kinds of amphidises in this sponge: — 1, large macramphidises, 2, 
small macramphidises, 3, large micramphidiscs, and 4, small micramphidiscs. 
Although the length frequency-curve of the large macramphidiscs has two 
summits, I do not distinguish two distinct groups among these spicules, because 
the depression between the two summits is but slight and because there are 
no notable morphological differences between the spicules to which the two 
parts of the curve on each side of the depression refer. 
The large macramphidiscs (Plate 86, figs. 1-6; Plate 89, figs. 31, 32; Plate 
91, figs. 1-6) are 370-550 uw long, most frequently about 425 4. The shaft is 
straight, cylindrical, and 19-27 » thick. It usually bears a few broad and low 
quite insignificant tubercles. Some of these are often arranged in an irregular 
verticil situated in the middle-part of the shaft, which is, at this point, usually 
slightly thickened to an inconspicuous central tyle, only 1-3 u, exceptionally 
as much as 6 », more than the adjacent parts in transverse diameter. Rarely 
the shaft bears a larger, cylindrical, terminally rounded spine, sometimes 28 yu 
long, and 10 u thick (Plate 86, fig. 4). I have never observed more than one 
such spine on the shaft of the large macramphidiscs. 
The terminal anchors are 120-170 » long and 200-256 » broad. The 
proportion of their length to their breadth is 100 : 139 to 100 : 196, on an average 
100 : 171.3. The proportion of the anchor-length to the total length of the 
spicule is 1 to 2.64.7, on an average 1 : 3.6. The anchors are usually composed 
of eight teeth. The teeth of the two anchors of the same spicule lie opposite 
each other in the same planes passing through the axis of the shaft. The indi- 
vidual teeth are about 25 » broad near the base, and pointed at the end (Plate 
89, figs. 31, 32). Their curvature is usually greater at the base and at the end 
than in the middle. The tip of the tooth is sometimes abruptly bent either 
inward (Plate 91, fig. 4) or, more rarely, outward (Plate 91, fig. 1). The teeth 
occasionally bear conspicuous, somewhat branch-like protuberances on their 
convex outer (Plate 91, fig. 3) or concave inner side (Plate 91, fig. 2). A well- 
marked depression can be made out, sometimes very clearly, on the apex of the 
anchor (Plate 91, fig. 4). 
The length frequency-curve of the small macramphidises has two summits 
separated by a rather conspicuous gap. The smaller ones, to which the part 
of the curve to the left of the depression refers, have a larger number of anchor- 
teeth than the larger ones, to which the part of the curve to the right of the 
_ depression refers. Two kinds of small macramphidises could therefore be 
distinguished. Since, however, the differences between them are not great and 
