278 
HYALONEMA (PRIONEMA) CRASSUM. 
in their basal part, but only slightly curved or straight in their distal part. 
The latter is either parallel to the shaft or diverges from it only slightly. 
Among the known species Hyalonema solutum F. E. Schulze 1 appears to be 
the nearest ally of the sponges above described. From this they differ by 
having much smaller pinules, stouter microhexactine rays, spined macramphi- 
disc-shafts, and serrated macramphidisc-teeth. The nearest ally appears to be 
H. (P.) crassum (infra). From this it differs chiefly: — by the absence of 
macramphidiscs with short and broad anchors and smooth teeth; by the 
anchors of the serrated macramphidiscs being somewhat differently shaped; 
by the presence of small macramphidiscs; by the smaller size of the largest 
micramphidiscs; by the absence of stout paratangential rhabds (tignules) in the 
superficial membranes; and by having smaller pinules. 
Hyalonema (Prionema) crassum, sp. nov. 
Plate 106, figs. 4-37; Plate 107, figs. 1-20; Plate 108, figs. 1-17. 
A larger and two smaller specimens of this species were trawled nearly under 
the equator at Station 4742 on 15 February, 1905; 0° 3.4' N., 117° 15.8' W. ; depth 
4243 m. (2320 f.); they grew on very light, fine Globigerina ooze; the bottom- 
temperature was 34.3°. They possess macramphidiscs with remarkably stout 
shafts and thick superficial amphioxes. To these peculiarities the specific name 
refers. 
Shape and size. The largest specimen (Plate 107 , fig. 16) has the shape of a 
low, thick-walled cup, irregularly circular in outline. The cup measures 36 mm. 
in transverse diameter and is 21 mm. high. Its wall is at the base about 9 mm. 
thick, near the margin about 6 mm. Its convex, outer, dermal face is fairly 
smooth. On the inner, concave, gastral face longitudinally (radially) extending 
grooves make their appearance. The margin of the cup is rounded. Just out- 
side this rounded margin, where it passes into the outer convex face, a slightly 
protruding but very distinct crest makes its appearance. This crest, which 
forms a complete ring round the cup, probably marks the boundary between the 
dermal and gastral parts of the surface. 
The two smaller specimens are similar, but more cake-shaped and respec- 
tively 24 and 21 mm. in maximum diameter. 
The colour of the sponge in spirit is light dirty brown. 
The skeleton. All the intact parts of the surface are covered with a dense 
F. E. Schulze. Hexactinellida. Ergeb. Deutsch. tiefsee-exped., 1904, 4 , p. 77, t. 31, fig. 14—22. 
