52 THE SPONGES. 



The specimen from Station 3399 has the shape of a wide, shallow cup 

 and is not laterally compressed. The cup, in which both base and edge 

 are preserved, is 53-63 mm. wide and about 20 mm. deep; the wall 3 mm. 

 thick near the centre and thinning out toward the edge. In the centre 

 of the cup the wall is steeper than elsewhere, and thus an inner basin is 

 marked off from a more peripheral region. The peripheral part of the wall 

 flattens out somewhat, tending toward the horizontal plane, and in one 

 re(»-ion is recurved much as in Schulze's figure of B. levis (Schulze, 1902, 

 Plate XIV. Fio*. 1). The inner surface of the cup, in the peripheral 

 reo-ion, is undulating, and the edge likewise undulating, as in Schulze's 

 fit»-ure. Viewed from the under surface, the base of the cup forms a well- 

 marked protuberance, to one side of which the sponge tissue has grown 

 round three Hyalonema root spicules, remnants of which remain half buried 

 in the wall. The fragments of root spicules lie close together, parallel to 

 one another and about parallel to the horizontal axis of the cup. They 

 are doubtless part of a Hyalonema root tuft to which the Bathydorus was 

 attached. 



The fragment dredged at Station 3399 is a plate-like piece 30 mm x. 

 25 mm. and about 2 mm. thick, including a part of the natural edge of the 

 sponge, 40 mm. long. 



In all the specimens both dermal and gastral surfaces exhibit fairly 

 abundant although scattered prostalia, projecting obliquely or radially 

 to a distance of from a few to 10 mm. The spicules are chiefly smooth 

 diacts, but in part large smooth hexacts with unequal rays, only one ray 

 of which projects. The rays of a single hexact may vary in length from 

 2 to 10 mm., the protruding ray being long. In addition both surfaces 

 are abundantly covered with the ends of slender diacts projecting 1-2 mm. 



Round the edge, numerous diacts project 1-2 mm., and scattered 

 diacts protrude through all distances up to about 5 mm. These scat- 

 tered spicules are pretty far, 5-10 mm., apart. The spicules project at 

 all angles from the edge, and nowhere constitute anything so definite as 

 a fringe. 



On both surfaces of the sponge, the rounded apertures of small canals 

 are abundant and plainly visible. The diameter of the canals is in general 

 less than, although reaching, 1 mm. 



The autodermal stauracts, Fig. 13, Plate 5, are abundant, the rays 

 overlapping so as to form a meshwork. The rays are cylindrical, or taper 



