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



where throughout the whole sponge. They have the form of thick hexacts, pentacts, 

 tetracts, triacts or cliacts, whose rays, uniformly thick, strong and cylindrical— exhibit 

 blunt or rounded ends, and are more or less abundantly covered with short, strong, 

 conical sjjines. These teeth or spines are either uniformly scattered over the whole 

 surface, or occur only on the distal ends of the several rays, the median and proximal 

 portions remaining smooth. As these peculiar spicules of the basal pad have been figured 

 in the case of Hyalonema sieboldii in Max Schultze's classic work on Hyalonematidse, 

 I have not devoted to them any special illustration. 



Of all the skeletal parts of Hyalonema sieboldii, the long spicules of the basal tuft 

 have been longest and most intimately studied. These basalia form a long loosely 

 wound strand, which measures .30 to GO cm. or more in length, and breaks up towards 

 the foot in a brush-like fashion. To the detailed descriptions of former investigators J 

 have but little new to add, and therefore refer to their accounts, especially to that of 

 Max Schultze.' He found in one tuft 200 to 300 separate spicules, of which the shorter 

 lay nearer the axis. The shape of the inferior extremity was certainly determined only 

 in the shorter forms. He observed a simple pointed termination, similar to that of the 

 superior extremity hidden within the sponge. Besides perfectly smooth forms, numerous 

 spicules occur with a tooth-bearing spiral ridge. TJie free margin of the latter projects 

 obliquely outwards and upwards, so that a similar direction is given to the leaf or nail- 

 like, pointed or slightly rounded spines which it bears. Interruptions of the spirals 

 sometimes occur, and these are often so regularly disposed, that the remaining portions 

 of the projecting ridges are alternately opposed to one another. 



On some very well-preserved (spirit) specimens collected by Dr. Hilgendorf in 

 Sagami Bay, Japan, I was able to study the very inferior extremity of many of the long 

 spicules of the tuft. It appeared that the spinose main portion of the spicule is followed 

 by a short, narrow, smooth neck, which bears terminally a solid, cap-like or hemispherical 

 thickening whose upper rounded margin exhibits eight recurrent teeth, forming an anchor- 

 like fiorure. 



2. Ilyaloiu^ma gi-acile, n. sp. (PL XXVII. figs. 14-23). 



This species of Hyalonema was dredged in the neighbourhood of the Philippine 

 Island Mindanao (lat. 8° 0' N., long. 121° 42' S., Station 211), from a depth of 2225 

 fathoms, and on a blue mud ground. Its body, which is approximately pear-shaj)ed, 

 measures 2 '5 cm. in length by 1'6 cm. in breadth. The upper end, which is somewhat 

 narrowed and transversely truncated, bears a delicate sieve-plate, while the lower, 

 conically pointed end runs out into a basal tuft, 1'5 mm. broad and about 3 cm. long. 

 The component spicules are not numerous, nor twisted, and they diverge but slightly 



' Diu Hvfiloiiemeii, Taf. ii. tigs. 1-7. 



