REPORT ON THE HEXACTINELLIDA. 199 



The skeletal elements of the gastral membrane and lining of the efferent canals agree 

 in many respects with those of the dei'mal area. The hypogastral loentacts are, however, 

 wanting, being either replaced by diacts or not at all. The autogastral pentact pinnies 

 generally resemble the dermals in form and length ; they are, however, throughout more 

 delicate and slim (PL XXVII. fig. 22). They are at once thickest and strongest near 

 the margins of the openings, and are seen to be more widely separated and more weakly 

 developed the further the canals are traced inwards. 



The long narrow diact marginalia in several layers, form a not very high, cuff-like 

 projecting marginal fringe. From the middle portion, which is distinguished by four 

 cruciate protuberances wdth axial canals, a smooth, gradually narrowing, terminally 

 pointed proximal ray extends inwards, while, in the opposite direction, an equally long, 

 or still longer distal ray, projects freely outwards in the same axis. The basal portion of 

 the latter is smooth, but the larger portion, on to the freely projecting terminal point, is 

 furnished with pointed, distally-directed lateral teeth, gradually decreasing in size. 



In the basal pad, strong short spicules occur, with from six to two thick, cylindrical 

 rays, whose terminal portions are frequently somewhat thickened, and always covered 

 with radially disposed, pointed, conical teeth. Of the apparently smooth basal spicules 

 which form a simple, untwisted tuft, but few are present, and these all broken. 



3. Hyalonema divergens, n. sp. (PI. XXVIII. figs. 1-11). 



This species of Hyalonema was dredged in Mid-Pacific, to the east of Maldon Island 

 (Station 271), lat. 0° 33' S., long 151° 34' W., from a depth of 2425 fathoms, on a 

 Globigerina ooze ground. In shape it resembles an inverted bell, with a slightly widened 

 terminal portion ; it possesses a length of 8 cm. and a maximum breadth of 6 '5 cm. (PI. 

 XXVIII. fig. 1). The superior margin of the transversely truncated terminal surface 

 bears a delicate spicule-fringe. The terminal surface itself is formed by a transversely 

 ,-tretched net, that is, by a typical sieve-plate. From the somewhat pointed lower end a 

 straight basal tuft projects. It is composed of parallel basal spicules, which are, for the 

 most part, broken somewhat short, and sometimes attain the thickness of almost a 

 millimetre. 



The only specimen procured is somewhat compressed, and in some places rubbed 

 away, so that it is impossible to make any definite statements as to the characters 

 of the lateral surface. Only here and there does a patch of uninjured skin persist. At 

 the inferior extremity of the body, where the long, strong spicules of the root-tuft freely 

 project, the often mentioned thick basal pad is seen. There is no trace of encrusting 

 Pali/thoa, but the general state of preservation makes it impossible to say with certainty 

 that the Pahjthoa were absent during the life of the sponge. 



The delicate net of the terminal sieve-membrane is raised from the marginal portion 



