86 THE VOYAGE OF H.M.S. CHALLENGEE. 



1. Ilolascus steUatus, n. sp. (PI. XIV. figs. 6-13; PI. XV. figs. 6-23). 



Station 325, east of Buenos Ayres ; lat. 36° 44' S., long. 46° 16' W.; depth, 

 2650 fotlioms ; bottom, blue mud. 



At the above locality, the specimen figured in PI. XV. fig. 6 was dredged, as also 

 the greatly injured fragment of a second specimen represented in PI. XV. fig. 14. 

 The two s^Decimens difi'er, moreover, not only in their size, but also in the individual 

 forms of the spicules, so that notwithstanding the general agreement, we have perhajjs 

 to deal with two difi'erent species. 



In the former specimen the almost cylindrical tube, which is slightly widened in the 

 middle (PL XV. fig. 6) is 8 cm. long and 13 mm. broad. Upon the upper transversely 

 truncated margin, a terminal circular pad projects somewhat outwards, and this supports 

 transversely the stretched retiform sieve-plate which has been figured by Wy ville Thomson 

 (PI. XV. fig. 6), but which is no longer preserved in the object before me. From their 

 inferior extremity, which is only slightly narrowed, there extends, somewhat to the side, a 

 badly-preserved tuft of fibres about 2 cm. in length. The outer surface of the wall, 

 which is from 1'5 to 2 mm. in thickness, appears to the unaided eye to be roughened 

 by small tubercles, while, with the help of a lens, numerous small pointed elevations 

 showing a uniform distribution and a regular arrangement may be observed in transverse 

 and longitudinal rows. On the inner side pit-like depressions about 1 mm. in breadth 

 likewise occur. 



The principalia, which constitute the groundwork of the quadrate lattice-like frame- 

 work of the tubular wall, are hexacts and pentacts with a distal radial ray. The long 

 longitudinal and transverse rays are so applied to each other that the transv^erse rays 

 come to lie altogether on the inner side of the longitudinally dii-ected rays. According 

 to the figure given by Wyville Thomson (PI. XV. fig. 7) it might be thought that the 

 lattice-like network lies close to the inner side of the wall of the tube, and that it 

 consists of nothing but pentacts. Such, however, is not the case. It extends, on the 

 other hand, between the inner and middle third of the thickness of the wall, and consists 

 for the most part of hexacts, between which pentacts with distal radial rays only here and 

 there appear. Numerous thin comitalia, with a variable number of rays, accompany the 

 transverse rays of the principalia. Near the margin of the body, outside the longitudinal 

 strands, long diacts also occur, with pointed upper ends, and with anchor-hooks on their 

 inferior extremities. These diacts are, as a rule, quite smooth above, but bear towards 

 the lower end barbs, which become gradually longer towards the end where the ray 

 passes into a conical pointed thickening, from which usually four, seldom more, anchor- 

 teeth project obliquely outwards and upwards (PI. XV. fig. 13). Projecting freely down- 

 wards for a greater or less distance they form the basal root-tuft. 



Among the parenchymalia we must also mention the long, thin, terminally pointed 



