HYALONEMA (SKIANEMA) AEQUATORIALE. 377 



Hyalonema (Skianemaj aequatoriale, sp. nov. 

 Plate 99, figs. 1-37; Plate 100, figs. 1-12; Plate 101, figs. 1-3. 



A single specimen of this species was trawled in the Eastern Tropical Pacific 

 at Station 4742 on 15 February, 1905; 0° 3.4' N., 117° 15.8' W.; depth 4243 m. 

 (2320 f.) ; it grew on a bottom of very light, fine Globigerina ooze; the bottom- 

 temperature was 34.3°. 



The locality where it was found lies nearly under the equator and to this 

 the name refers. 



Shape and size. The single specimen is somewhat lacerated and fragmentary. 

 It now appears (Plate 99, fig. 17) flattened and elongate. One end is rounded. 

 At the other it terminates with a nearly straight margin vertical to the two longer 

 sides. It is 71 mm. long, 45 mm. broad, and has a maximum thickness of 15 mm. 

 In life it was probably not much thinner than broad. The straight terminus is 

 the upper gastral face. It is slightly depressed in its middle-part, from which 

 a gastral cone arises. This cone is surrounded by thin, more or less vertical, 

 radiating lamellae, between which extend extensive cavities, now much com- 

 pressed. The rounded end is the lower, and from it doubtlessly arose in life 

 a stalk, which has, however, been completely lost. 



The colour in spirit is whitish brown. 



Traces of elongate flagellate chambers about 75 ^ broad can be made out here 

 and there in the sections. 



The skeleton. A dense spicule-fur covers all intact parts of the surface 

 (Plate 101, figs. 1, 2a, 3). Between the basal parts of the distal raj^s of the 

 superficial pinules forming this fur are met small macramphidiscs, generally 

 with the shaft vertical to the surface of the sponge (Plate 101, fig. 2c). The 

 superficial membranes are supported by the lateral rays of the (dermal and 

 gastral) pinules, and the (hypodermal and hypogastral) pentactines; paratan- 

 gential rhabds also occur in it in considerable numbers (Plate 101, fig. 3). Just 

 below the surface numerous large macramphidiscs are found (Plate 101, fig. 2d). 

 A loose bundle of large amphioxes occupies the axial part of the sponge. This 

 bundle extends completely into the gastral cone. More or less radially extending 

 rhabds occur in the choanosome. Most of the rhabds in the superficial mem- 

 branes and in these bundles are amphioxes; some diactine styles or tylostyles, 

 however, also occur. Microhexactines are scattered throughout the choano- 

 some in large numbers. Large and small micramphidiscs are also found in it. 

 These spicules are, however, rather rare. In the interior of the gastral cone 

 a good many spheres have been observed. 



