356 HYALONEMA (OONEMA) SEQUOIA. 
since the extreme forms are connected by numerous transitions, I shall here 
describe both together. 
The small macramphidiscs (Plate 86, figs. 7, 27-34; Plate 89, fig. 15d; 
Plate 90, figs. 1-10) are 90-195 » long, most frequently about 1644. The 
shaft is straight, smooth, cylindrical, and 5.5-16.5 4 thick. The terminal 
anchors are 39-100 » long, and 55-174 » broad, usually 70-150 u. The pro- 
portion of anchor-length to anchor-breadth is 100 :120 to 100:178, on an 
average 100: 149. As has been stated above, these anchors are about half as 
long as the whole spicule, sometimes a little shorter than that, more frequently 
a little longer. Each anchor is composed of five to thirteen teeth. The larger 
amphidises of this kind, that is those to which the part of the length frequency- 
curve culminating at 164 » refers, have five to ten, usually eight teeth; the 
smaller, to which the part of the curve culminating at 93 u refers, have eight to 
thirteen, usually eleven teeth. The two terminal anchors of the same spicule 
are composed of the same number of teeth. The teeth of the terminal anchors 
extend in planes passing through the axis of the spicule. The anchor-teeth 
planes of one anchor enclose equal angles with their neighbours, each 360 degrees 
divided by the number of teeth. The anchor-teeth planes of the other anchor 
of the same spicule allernate regularly with these in such manner that they 
divide each angle into two equal parts (halves). Thus the tips of the teeth of 
the two opposite anchors are not opposite but alternate. 
The individual anchor-teeth are curved, either uniformly or, more fre- 
quently, less in the middle-part than at the base and at the tip. The outer 
contour of each tooth is abruptly curved inwards at the distal end. The teeth 
are T-shaped in transverse section. Their outer (upper) part, which corresponds 
to the upper stroke of the T, has the shape of a curved band increasing in breadth 
distally to a point three quarters of the length of the tooth from its base. Here 
the tooth is 9-30 » broad. The end-part of the tooth, lying beyond this point 
of maximum breadth, is simply rounded (Plate 90, figs. 1, 3, 7, 9). The inner 
(lower) part of the tooth, which corresponds to the lower stroke of the T, is a 
thick keel, uniformly decreasing in height distally. The end-part of the upper 
(outer) band-shaped portion of the tooth bends down around the end-part of 
the keel on all sides except the axial, so that, viewed in profile, the end-part of 
the whole tooth becomes strikingly similar to a crow’s beak (Plate 90, figs. 4, 6, 
8, 10). 
Slightly abnormal small macramphidiscs with one or more somewhat irregu- 
lar teeth, like the one represented (Plate 90, figs. 5, 6), have repeatedly been met. 
