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) arc remarkably numerous. The 

 terminal anchors are 9-38 m long and 8-39 m broad. The proportion of their 

 length to their lireadth is 100 to 81-125, on an average 100 : 94. As stated 

 above, the micramphidiscs of different sizes, are very similar in shape, the differ- 

 ences in the proportions of their difTerent dimensions being only slight. In 

 the micramphidiscs over 80 m 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 micramphidiscs under 50 yu 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^, on an a^'erage 1 : 3.16. The curvature of the anchor-teeth decreases dis- 

 tally. This decrease is more marked in the smaller than in the larger micram- 

 phidiscs. The teeth are 4-7 ^l broad, and rounded at the end; their tips are 

 usually nearly parallel. 



This sponge is obviously most closely aUied to Hyalonema {Oonema) sequoia. 

 From this it differs by the absence of the smaller kind of smaU macramphidiscs 

 with numerous anchor-teeth ; by the presence of narrow-anchored small macram- 

 phidiscs, 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 



