106 
LANUGONYCHIA FLABELLUM. 
The (hypodermal and hypogastral) pentadines (Plate 13, figs. 10, 12, 13, 
16b) have an apical (proximal) ray 0.6-1 mm. long, and lateral (paratangential) 
rays 400-800 /*. The lateral rays of the same spicule are more or less unequal, 
the longest usually being 150-250 n longer than the shortest. All the rays are 
straight, conic, blunt, and 20-40 n thick at the base. The end-parts of the 
lateral rays bear quite numerous sharp-pointed spines. Proximally these spines 
become more blunt, lower, and less numerous, and they pass gradually into 
slight, hardly perceptible, flattened protuberances, finally disappearing alto- 
gether. The proximal parts of the lateral rays are smooth. 
Pentadines with very long apical rays (Plate 13 , figs. 9, 16a) have also been 
observed. The apical (proximal) ray is in these spicules 3-9 mm. long. The 
lateral rays are usually broken; one intact one (Plate 13 , fig. 9) was 1.85 mm. 
long and curved. These spicules may be foreign. Some of them are strongly 
corroded. 
A few large sword-like hexactines with the rays of one axis differently devel- 
oped from the rays of the other two axes have also been observed. The two rays 
in the differentiated axis represent the blade and the handle of the sword. The 
former is very long and broken off in the spicules observed. The latter is 165 n 
long and covered with spines. At the base it is 24-30 n thick and either cylindri- 
cal or terminally thickened, club-shaped. The other four rays, which represent 
the guard of the sword, appear to be long and equal among themselves. They 
were all broken off in the sword-like hexactine observed. These spicules seem 
to take part in the formation of the skeleton of the stalk; it is possible, however, 
that they are foreign. 
The small hexadines arid hexadine-derivates (Plate 12 , figs. 24-34; Plate 13 , 
figs. 5c, 28) always have fairly straight rays, but are, apart from this, remarkably 
variable and irregular. In the first place the angles between adjacent rays are 
not, as is generally the case in hexactinellid spicules, invariably 90°. In a good 
many of the tetractine (stauractine) (Plate 12, fig. 33), the triactine, and particu- 
larly the diactine (Plate 12 , fig. 26; Plate 13 , fig. 5c) forms, other than right 
angles are enclosed by them. This angular irregularity is particularly pro- 
nounced in some diactines which appear as variously opened compasses (Plate 12, 
fig. 26; Plate 13 , fig. 5c). In the second place one to five of the rays may be 
reduced to mere terminally rounded protuberances arising from the centre of 
the spicule. Finally the reduced rays and, to a certain extent, also the fully 
developed rays of the same spicules are frequently unequal among themselves. 
In spite of this variability there are, however, absolutely no transitions between 
the reduced and the properly developed rays. 
