HYALONEMA (PHIALONEMA) P ATE R I FE RUM . 
363 
stalk 330 mm. long, and 6 mm. thick at the base. Another is saucer-shaped, 
40 mm. deep, 85 mm. long, and 65 mm. broad. The dermal membrane and the 
central part of the gastral membrane are reticulate. The marginal part of the 
latter is perforated by efferent pores 1.5 mm. wide. The specimens of form B 
are, according to the same author ( loc . cit.), flattened. One is saucer-shaped, 
15 mm. deep, 80 mm. long, and 60 mm. broad; the other a fragment, probably 
of a similar sponge. The surface is continuous and smooth, not reticulate. 
The specimen of form C (Plate 52 , fig. 20) appears as a broad and low, conic cup. 
It is 52 mm. high, 61 mm. long, and 54 mm. broad. The central part of the 
cup-wall is very thick. Distally it thins out to a sharp margin. The lower 
truncate end, from which in life the stalk probably arose, is lacerated. No trace 
of a stalk or a gastral cone can now be detected in the specimen. The outer 
(dermal) surface of the cup-wall is much damaged, and appears irregular and 
very porous. The inner (gastral) surface is, for a considerable extent, still 
covered by the gastral membrane. This is perforated by rather large broad- 
oval apertures. The specimen of form D (Plate 52 , fig. 21) is a slightly curved 
lamella with rounded margin, 45 mm. long, 36 mm. broad, and uniformly 10 mm. 
thick. The larger part of the surface is smooth. On the concave (gastral) 
face the superficial (gastral) membrane is preserved. There is no gastral cone. 
A portion of the margin of the sponge is much lacerated. From this part the 
now missing stalk probably arose. The specimen of form E (Plate 51, fig. 1) 
is a porous, lacerated, lamellar fragment, and measures 60 by 32 by 8 mm. 
The specimen of form F is likewise very fragmentary. It appears as an irregular, 
porous lamella and measures 33 by 29 by 4 mm. 
The colour of the specimens of forms C and D in spirit is brown with a 
greenish tinge, that of form E reddish brown, and that of form F whitish. 
Canal-system. The efferent canal-systems are, according to Wilson (loc. cit.), 
in form A 5-10 mm. wide, and traceable quite down to the basal part of the 
sponge. In form D the flagellate chambers appear to be elongated, sac-shaped, 
irregularly curved, and 70-90 m broad. 
The skeleton. The surface of the body is covered with a dense pinule-fur 
(Plate 52 , figs. 22, 23). In the forms A and B examined by Wilson (loc. cit.) the 
fur of the dermal face is composed of pinnies with distal rays of moderate and 
fairly equal length. On the gastral face pinules with much longer distal rays 
lie scattered between the masses of pinules with moderately long distal rays. 
In the forms C and D, pinules with long distal rays are scattered among the ordi- 
nary ones also in the fur of the dermal face. So far as the fragmentary state 
