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 ^ appears to be 

 the nearest ally of the sponges above described. From this they difTer 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. Deutseh. tiefsee-exped., 1904, 4, p. 77, t. 31, fig. 14-22. 



