HYALONEMA (OONEMA) DENSUM. 341 
central tyle, and a good many similar spines are found also on other parts of 
the shaft. The spines are more abundant in the larger than in the smaller forms, 
and in some of the former (Plate 94, figs. 6, 7, 13) are remarkably numerous. The 
terminal anchors are 9-38 » long and 8-39 » broad. The proportion of their 
length to their breadth is 100 to 81-125, on an average 100 :94. As stated 
above, the micramphidises of different sizes, are very similar in shape, the differ- 
ences in the proportions of their different dimensions being only slight. In 
the micramphidises over 80, in length the proportion of anchor-length to 
anchor-breadth is 100 to 89-114, on an average 100 : 95, and the proportion of 
the anchor-length to the length of the whole spicule 1 to 2.6-3.2, on an 
average 1 :2.9. In the micramphidises under 50 » in length the proportion of 
anchor-length to anchor-breadth is 100 to 78-125, on an average 100 : 90.5; 
and the proportion of the anchor-length to the length of the whole spicule 1 to 
2.8-4, on an average | :3.16. The curvature of the anchor-teeth decreases dis- 
tally. This decrease is more marked in the smaller than in the larger micram- 
phidises. The teeth are 4-7 » broad, and rounded at the end; their tips are 
usually nearly parallel. 
This sponge is obviously most closely allied to Hyalonema (Oonema) sequoia. 
From this it differs by the absence of the smaller kind of small macramphidises 
with numerous anchor-teeth; by the presence of narrow-anchored small macram- 
phidises, and superficial pinules with long strongly divergent spines on the 
proximal part of the distal ray; and by the smaller size of several kinds of its 
spicules, chiefly the superficial pinules. 
Hyalonema (Oonema) densum, sp. nov. 
Plate 94, figs. 34-42; Plate 95, figs. 1-20; Plate 96, figs. 1-14. 
One specimen of this species was trawled in the Eastern Tropical Pacific 
at Station 4649, on 10 November, 1904; 5° 17’ S., 85° 19.5’ W.; depth 4086 m. 
(2235 f.); it grew on a bottom of sticky, gray mud; the bottom-temperature 
was 35.4° 
The name has reference to the remarkable density of the sponge. 
Shape and size. The single specimen (Plate 95, fig. 4) appears as an inverted 
cone cut off obliquely and considerably extended at one side above. The upper 
portion protrudes on this side like a bulging rim for a distance of 8 mm. The 
sponge is 57 mm. high, and the regularly oval upper face 46 mm. long and 39 
mm. broad. This upper face, which is to be considered as the gastral, is convex 
