342 
HYALONEMA (OONEMA) DENSUM. 
and perforated by numerous broad-oval efferent apertures 0.2-0. 9 mm. wide 
(Plate 95, fig. 3). A pointed, very eccentrically situated gastral cone 8 mm. 
high and, at the base, 6 mm. thick arises from it. The conical body is slender 
and has no pores visible with the unaided eye. Its surface is to be considered 
as the dermal face of the sponge. Its lower end is torn off. 
The colour in spirit is dirty light brown. 
Canal-system. In the choanosome more or less radial canals, sometimes 0.8 
mm. wide, are observed. Indications of elongate, perhaps tubular, flagellate 
chambers 30-70 ^ broad are observed in the sections. 
Skeleton. The whole of the surface is covered with a dense pinule-fur 
(Plate 95, figs. 1, 2). Between the proximal parts of the freely protruding 
distal rays of the pinules forming it are met small macramphidiscs, mostly 
with the shaft in a radial position. The dermal and gastral membranes are 
supported by the lateral rays of the superficial pinules, paratangential centro- 
tyle amphioxes, and the lateral rays of hypodermal or hypogastral pentactines. 
Masses of microhexactines and some small macramphidiscs occur in and just 
below these membranes. A good many large micramphidiscs, dense masses 
of microhexactines, and a few canalar pinules occur in the canal-walls. The 
micramphidiscs appear to be restricted to the efferent canals. Apart from these 
canalar spicules, one finds in the interior a few large macramphidiscs, hexactine 
megascleres, and small micramphidiscs, numerous ordinary small choanosomal 
amphioxes, and some large axial amphioxes forming the upper continuation 
of the stalk. In the lower part of the sponge-body numerous acanthophores 
are added to these spicules. These extend remarkably far up. The upper 
acanthophores have long, slender, and usually fairly straight and not very spiny 
rays. In the lower acanthophores the rays are either reduced in length, stout, 
and very spiny, or long, slender, not particularly spiny, and more or less, often 
considerably curved. 
The dermal pinules have a distal ray 230-855 m long. The length frequency- 
curve of their distal rays has a very marked depression at about 530 (x, and two 
perfectly distinct elevations at 370 and 650 n. I therefore distinguish two kinds 
of dermal pinules, a large and a small. 
The large dermal pinules (Plate 95, figs. 1, 15, 19, 20) are pentactine. Their 
distal ray is straight, 560-855 m long, most frequently about 650 n , and 12-23 m 
thick at the base. It ends with a short and stout terminal cone, and bears spines 
which extend quite down to its base, or nearly so. The lowest spines are very 
short, stout, conical, and vertical; distally the spines become larger and more 
