368 
HYALONEMA (PHIALONEMA) PATE RIFERUM. 
acanthophores with rays 15-30 m thick at the base. The diactines are here 
550-720 n long, the tri- to pentactines 290-720 n in maximum diameter. The 
rays of these spicules are somewhat irregular, wavy in outline, and often slightly 
curved. They usually taper distally. The end itself is frequently slightly 
thickened and terminally rounded. The basal and middle-parts of the rays 
are smooth, their end-parts, for a short distance, densely spined. 
Among the microhexactines (Plate 50 , figs. 9, 10; Plate 51 , figs. 23-28; 
Plate 52 , figs. 1 , 2 ) forms with small spines and strongly curved rays, and forms 
with larger spines and only slightly curved or straight rays, can be distinguished. 
The former are usually much smaller than the latter. The larger forms with 
straight rays are connected by transitions with the pinules. The rays of the 
microhexactines are in the forms A and B, according to Wilson ( loc . cit.), 
30-80 jj. long, and in the small ones with curved rays 2 n thick. In the forms 
C, D, E, and F the rays of the microhexactines are, at the base, 1-3.5 n thick, 
usually 1.5-2. 5 n. Those measured of form C were 55-80 n in diameter, of 
form D 64-128 n, of form E 55-150 n, and of form F 59-138 The small 
microhexactines with curved rays are regular, the six rays of the same spicule 
being equal in size and curvature, all straight at the base, and uniformly curved 
in their distal part through an angle of 45°-135°. The direction of curvature 
in opposite rays is usually opposite (Plate 51 , figs. 23, 24, 26, 28). In the rare, 
large microhexactines with curved rays, the curvature is irregular, and different 
in the different rays of the same spicule (Plate 51 , fig. 25). In the large micro- 
hexactines with nearly straight rays, the six rays are generally equal. Any 
curvature observable in them is restricted to their distal part. 
Of amphidiscs four forms can be distinguished: — large macramphidiscs, 
small macramphidiscs, large micramphidiscs, and small micramphidiscs. The 
large and small macramphidiscs are not clearly separated biometrically (accord- 
ing to their length frequency) or morphologically. Nevertheless there is, in 
all the four forms examined by me, a deep depression at about 100 n in the 
frequency-curve pertaining to these spicules, which renders it advisable to dis- 
tinguish them. The macra*mphidiscs shorter than 100 m I consider as small, 
those longer as large ones. The macramphidiscs under 100 n in length, that is 
the small ones, have relatively longer anchors and fewer anchor-teeth than 
those over 100 n in length, that is the large ones. The small macramphidiscs 
are clearly distinguished from the large micramphidiscs morphologically, the 
former having stout and smooth or nearly smooth shafts and broad terminal 
anchors; the latter slender and strongly spined shafts and narrow terminal 
