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



like openings whicli led into the foni' subjacent cavities. In this lid, and in the conical 

 terminal knob, the same fir-tree-like amphidiscs occurred as in the external skin. 



From my own examination of the specimen in Professor 0. Schmidt's possession, which 

 was originally investigated by Marshall, I am able to corroborate the essential results of 

 Marshall's research, and I shaU therefore only confine myself to extending and completing 

 the latter. 



The parenchyma proper in the above-described Hyalonema is supported by medium- 

 sized, smooth, regular oxyhexacts, beside which numerous smooth, straight, or curved 

 diacts occur, with or without central swellings. These have been already figured in 

 detail by Marshall. Small oxyhexacts with straight roughened rays — and these only — 

 occur in moderate abundance (PL XXXIV. fig. 4). In the dermal skeleton the familiar 

 smooth hypodermal pentacts occur, as also autodermal pentact pinuli with somewhat long 

 terminally toothed basal rays, and with a freely projecting pointed distal, about 0"24 mm. 

 in length, and beset with long oblique curved spines (PI. XXXIV. fig. 6). Eoundish 

 amphidiscs of various form and size, of which the largest have an average length of 0"2 mm., 

 also occur. They are characterised by the possession of a flat, short, terminal umbel on 

 either side, with six simple hook or claw-shaped, narrow rays, not terminally broadened. 

 The moderately strong axial rod bears isolated hemispherical nodes, four of which, usually 

 somewhat more strongly developed, are cruciately disposed in the centre (PI. XXXIV. 

 fig. 2). An amphidisc of this type, in process of formation, is figured in PI. XXXIV. 

 fig. 7. Besides these typical six-rayed large amphidiscs, others half as large occur, with 

 long, campanulate, narrow, eight-rayed umbels, the slender rays of which almost meet, 

 diverging somewhat laterally towards one another. The narrow axial rod has a central 

 nodule (PI. XXXIV. fig. 3). Still smaller forms whose umbels with eight or more rays 

 are short and hemispherical (PL XXXIV. figs. 5, 8), occur abundantly. In the basal pad 

 of the lower end of the body strongly developed spicules occur, variously provided with 

 rays from six to two in number. These truncate rays are thickly studded with spines or 

 teeth from the ends to within a varying distance of the centre (PI. XXXIV. figs. 10, 11). 

 The tuft of spicules is composed solely of long spicules, which bear toothed ringed 

 ridges. These are either broken oS" inferiorly, or continued into a club-shaped or 

 hemispherical four-toothed anchor with four strong, backwardly bent, narrow, pointed 

 teeth (PL XXXIV. fig. 9). 



Among some Hexactinellids of the "Porcupine" Expedition which I obtained through 

 the Challenger Ofiice, I found a specimen with characters exactly corresponding to those 

 above described. This was obtained from Station 47 of the " Porcupine " Expedition, 

 from a depth of 542 fathoms. The extended spindle-shaped form had a total length of 

 4 "5 cm. The body proper, which was about 5 mm. in thickness, occuj^ied 3 cm.; and 

 was continued superiorly into an apex, while the narrowed lower end bore a colony of 

 three or four Pcdythoa polypes, embracing the basal tuft for 2 mm. ' The spicules both of 



