368 



which portion the body is 13 — 31 mm broad and whence it narrows 

 inferiorly to the basal pad. Entire body 50 — 60 mm long. The twisted 

 root-tuft , more or less covered with Palythoa , is rather slender and 

 may be as long as 400 mm. The oscular margin, unfurnished with a 

 cuflf, is blunt-edged or even entirely rounded oiF. The internal canals 

 open on the slope of the oscular area by irregularly distributed, com- 

 paratively small openings. The entire external surface of the body is 

 so very densely covered with pinuli, that it presents a compact, frosted 

 appearance, only the denuded places showing a reticular pattern. Of 

 the different forms of spicules, I limit myself to mentioning the follow- 

 ing points: 



Dermal pinuli 0,23 mm high; basal cross 0,08 mm broad. Their 

 distal ray, with obliquely set, well-developed spines, is genuinely club- 

 shaped, broadest (0,045 mm) at the lower end of the uppermost V4- 

 A rounded axial cone just projects out of the last whorl of spines at 

 the upper end. — Macramphidisc resembles that of H. Sieboldi, 

 0,32 mm long, 0,13 mm broad; umbel usually 7 rayed, about 1/3 as long 

 as the entire spicule. — Mesamphidisc 0,17 mm long and 0,06 mm 

 broad, or smaller, umbel longer than 1/3 the entire spicule. — Micr- 

 amphidisc as small as 0,05 mm in length and 0,025 mm in breadth. 

 Micro-oxyhexacts abundant; arms straight, weakly rough, 0,034 — 

 0,05 mm long. 



H. Owstoni seems to occur, not uncommonly, together with H. 

 apertum at more than 200 fathoms depth. 



Hyalonema clathratum sp. nov. 



Body approximately pear-shaped, apple-size or smaller. Diameter 

 of oscular area shorter than the greatest breadth of the body ; sieve- 

 plate more or less differentiated; oscular margin usually rounded off, 

 sometimes with cuff-like fringe. Surface distinctly latticed in wet 

 state, but downy or loosely frosted when dry. E-oot-tuft rather slen- 

 der, may be as long as 345 mm; always with Palythoa. 



The dermal pinuli resemble those of H. Owstoni, but decidedly 

 more slender, being 0,26 mm high and the distal ray 0,04 mm broad 

 at the broadest portion; basal cross 0,01 mm broad. — Macramphidisc 

 0,25 mm long, 0,12 mm broad; umbel shaped like that oî H. Sieboldi, 

 5 or 6 rayed, about 1/3 the length of the entire spicule. — Very cha- 

 racteristic of this species are the mesamphidiscs that abundantly occur 

 in the dermal membrane. They are barrel-shaped, 0,09 mm long and 

 0,04 mm broad, or smaller, the rays of the two umbels touching at 

 the equator. — Micramphidiscs as small as 0,0133 mm inlenght. — 

 Micro-oxyhexacts with straight arms 0,034 — 0,084 ram long. Larger 

 micro-oxyhexacts are rough, while smaller ones are smooth 



