368 HYALONEMA (PHIALONEMA) PATERIFERUM. 



acanthophores with rays 15-30 fi thick at the base. The diactines are here 

 550-720 /x long, the tri- to pentactines 290-720 /i in maximum diameter. The 

 raysi 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 (U 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 ^ thick, 

 usually 1.5-2.5 n. Those measured of form C were 55-80 fi in diameter, of 

 form D 64-128 m, of form E 55-150 fi, and of form F 59-138 n. 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 /i in the 

 frequency-curve pertaining to these spicules, which renders it advisable to dis- 

 tinguish them. The macramphidiscs shorter than 100 ix I consider as small, 

 those longer as large ones. The macramphidiscs under 100 ^i in length, that is 

 the small ones, have relatively longer anchors and fewer anchor-teeth than 

 those over 100 ix 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 



