214 THE VOYAGE OF H.M.S. CHALLENGER. 



these diacts with spinose terminal portions four cruciate hemispherical tubercles usually 

 occur. 



This species, Hyalonema thomsoni, differs from Hyalonenui lusitanicum, Bocage, not 

 only in general form and in the long projecting cone, but more especially in the large 

 amphidiscs with short narrow umbel rays, and in the absence of smaU oxyhexacts with 

 curved rays. 



Though I have no hesitation in including the three forms described above within 

 the one species, Hyalonema thomsoni, Marshall, I am in doubt as to a specunen of 

 Hyalonema dredged near the Azores (Station 73, lat. 38° 3' N., long. 31° 14' W.), at a 

 depth of 1000 fathoms, from a Pteropod ooze ground. This fragment, which has a total 

 length of only 3 cm., represents the lateral portion (about one-third) of a pear-shaped body, 

 about 8 mm. in breadth at the upper end, while the inferior portion narrowed to 2 mm. 

 projects as a broken tuft of few spicules. The superior extremity of the body is not 

 preserved. 



The parenchymal spicules consist of smooth oxydiacts of various lengths, with or \dth- 

 out central tubercles, and of moderately large smooth oxyhexacts and smaller forms ^-ith 

 straight somewhat roughened rays, — all exactly agreeing with those already described in 

 Hyalonema thomsoni. The hypodermal smooth oxypentacts and the somewhat slim auto- 

 dermal pinuli of the skin do also not differ essentially from those of Hyalonema thomsoni, 

 and the same may be said of the substantial spicules of the basal pad (PL XXXIV. figs. 15, 

 17), or of the long spicules of the root-tuft, distinguished by theu- four-toothed terminal 

 anchors (PL XXXIV. fig. 16), which exhibit an axial cross. 



Only the amphidiscs, still discoverable in the small and isolated remnants of the skin, 

 are somewhat divergent from those of the specimens of Hyalonema thomsoni, in the 

 apparent absence of the large form bearing short hemispherical terminal umbels with six or 

 eight narrow hook-shaped umbel rays, and in such slight differences in the form of the small 

 amphidiscs, as may be discovered by inspecting PL XXXIV. figs. 12, 13, 14. Since the 

 apparent absence of the large amphidiscs may very probably be referred to the incom- 

 pleteness of the specimen in which the skin was almost gone, and since besides the small 

 divergent amphidiscs exactly congruent forms also occur, there seems no reason to erect a 

 separate species for this fragment, and I therefore content myself with designating it 

 Hyalonema thomsoni, var. exiguum. 



2. Hyalonema (Stylocalyx) apertum, n. sp. (Pis. XXXVII., XXXVIIL). 



In the Sagami Bay, west of Yokohama in Japan (Station 232, lat. 35° U' K, 

 long 139° 28' E.), from a depth of 345 fathoms and a green mud bottom, several 

 specimens of Hyalonema were dredged. In some of these the body is still well preserved, 

 but in most only the basal tuft and the Palythoa incrustation remain. The body of the 



