REPORT ON THE HEXACTINELLIDA. 217 



in the specimen figured by Max Seliultze on Taf. i., 13 cm., while the root-tuft is 48 cm. 

 long and 1'5 cm. broad. I wish, however, to lay special emphasis on this, that in 

 Hyalonema affine the dermal skeleton (partly rubbed off however, though not to such an 

 extent as Max Schultze describes) exhibits peculiar characteristics. From the lower end 

 of the sponge body, from the position where the axial tuft enters, numerous longitudinal 

 strands, 0'5 mm. in breadth, arise, dividing repeatedly and anastomosing with one another, 

 becoming gradually narrower in so doing, and I did not observe these longitudinal strands 

 in any other specimen of Hyalonema, although I examined a considerable number in 

 various states of preservation. The strands are composed of uniaxial, decidedly long 

 (8 cm.) pliable spicules which frequently intersect. At the point of intersection there 

 is a tolerably constant occurrence of a spicule with dimensions which neither I nor 

 Max Schultze have ever found in Hyalonema sieboldii, namely, with an axial length of 

 fully 3 mm. The intersecting bundles lie in the direction of the axes. Between these 

 strands there is a further dermal skeleton, but this in no way diflfered from that of the 

 other specimens. Similarly the afferent apertures, and indeed the rest of the sponge- 

 tissue, agreed both in macro- and microscopic characters with Hyalonema sieboldii, though 

 the apertures were not so abundantly present. It seemed to me, however, that the great 

 differences in size, and especially the peculiar character of the dermal skeleton, justified 

 the erection of a new species, closely related to Hyalonema sieboldii." 



According to this description, which was of course based on a single, dry, and probably 

 not very well preserved specimen, it seems to me possible that the form above described 

 as Hyalonema apevtum may be identical with Marshall's Hyalonema affine, and I have 

 indeed hesitated long whether I should adopt the older designation. There is, however, 

 in Marshall's diagnosis no mention of some of the peculiarities which are t}^ical and 

 characteristic of Hyalonema apertum, especially the complete absence of the terminal 

 sieve membrane, while the character especially emphasised by Marshall, namely, the 

 presence of intersecting bundles of long uniaxial spicules below the skin of the dried 

 specimen, occurs also in various other species of Hyalonema (though not in Hyalonema 

 sieboldii, owing to the presence of countless commensal polypes), so that no certain and 

 exclusive character seems to remain to Hyalonema affi^ne. The dimensions of the body 

 or of the basal tuft cannot be regarded as in any way determinative. 



Since, then, it is not probable that Hyalonema affine, Marshall, is identical with 

 my Hyalonema apertum, I prefer to retain for the time the latter title. 



3. Hyalonema {Stylocalyx) deptressum, n. sp. (Pis. XXXV., XXXVI. ). 



In the Mid-North Pacific, north of the Mellish Islands (Station 246, lat. 36° 10' N., 

 long. 178° 0' E.), from a depth of 2050 fathoms and a Globigerina ooze ground, several 

 specimens of Hyalonema were dredged, which in general form differ markedly from the 



(ZOOL. CHAl.L. EXP. — PART LIII, — 1887.) Ggg 2S 



