HYALONEMA (PRIONEMA) CRASSUM. 
283 
both towards the base and towards the tip. The end of the tooth is simply 
rounded. From the lateral margins of the teeth pointed triangular protuberances 
arise, which stand close together and render these margins serrated. The saw- 
teeth are, in the middle-part of the tooth, about 1 ^ high, 2 broad, and vertical. 
Distally they become narrower and smaller and more and more directed back- 
wards (Plate 107, figs. 17-20). The rounded distal ends of the teeth are smooth. 
The large micramphidiscs are 42-61 ^ long, most frequently about 52 //. 
Their length frequency-curve is rather broad and irregular in so far as it exhibits, 
besides the main summit at about 52 n, another insignificant one at about 63 m- 
The shaft of these amphidiscs is straight, spiny, sometimes centrotyle, and 1.5- 
2.3 m thick. 
The terminal anchors are 17-22 m long. The whole spicule is 2.2-3 times 
as long as its anchors. The maximum anchor-breadth is 9-14 ,u. The end- 
breadth is equal to the maximum breadth or slightly smaller, sometimes as much 
as 4 yu. The proportion of anchor-length to anchor-breadth is 100 to 53-72, 
on an average 100 : 62. 
The individual teeth, which arise vertically from the shaft, are strongly 
bent in their basal part and only slightly bent or nearly straight in their distal 
part, so that their tips are nearly parallel or slightly convergent. 
The small micramphidiscs (Plate 106, figs. 13-25) are 13.5-36 m long. Their 
length frequency-curve is rather broad and irregular. It exhibits two equally 
high main summits at about 18.4 and 22.1 yu, and one insignificant summit at 
about 27 yU. The shaft of these amphidiscs is straight, cylindrical, 0.8-1. 2 ^ 
thick, rough or smooth, and usually centrotyle. The tyle, which exceeds the 
adjacent parts of the shaft 0.2-1 ,u in transverse diameter, is often a good distance 
away from the middle of the length of the spicule. 
The terminal anchors are 3.5-14 yu in length, a fifth to a third of the whole 
spicule, and 5-9 m broad. The proportion of anchor-length to anchor-breadth 
is 100 to 61-162, on an average 100 : 119.4. The largest of these small micram- 
phidiscs, that is those over 30 m in length, are transitional to the large ones above 
described, not only in respect to size, but also in respect to anchor-shape. The 
proportion of anchor-length to anchor-breadth is in these spicules on an average 
100 : 65. In all the small micramphidiscs, that, is in those under 30 n in length, 
the anchors are broader than long, the average proportion of anchor-length to 
anchor-breadth being in these spicules 100 : 125.6. 
The anchor-teeth of these spicules are generally strongly and rather abruptly 
bent at a point a third of their length from the base, and only slightly curved 
