REPORT ON THE HEXACTINELLIDA. 153 



without central nodes. The somewhat roughened or tul^ercled terminal portions are 

 rounded ott', or not unfrequently slightly club-shaped at their extremities. Between 

 these a large number of oxyhexasters occur with long, slim, but roughened terminal rays, 

 which vary considerably in number. The principal rays are much sliortened, and this 

 goes so far in some hexasters, that the spicule has quite the appearance of a simple, many- 

 rayed star (PI. LIX. fig. 2). A slight irregularity frequently occurs at the base of these 

 rays, in the occurrence of a slight union or something of that nature, which also points 

 to the reduction above referred to. The presence of these star-shaped pareuchjTnal 

 spicules led me to give this form of Bathydorus the specific title stellatus. Finally, in 

 the parenchyma, I have observed the isolated occurrence of minute delicate discohexasters, 

 in wdiich each of the six short principal rays bears, on a terminal expansion, three to six 

 long diverging terminal rays with a toothed terminal portion (PI. LIX. fig. 4). 



The dermal skeleton contains medium-sized, smooth, hypodcrmal oxypentacts, with 

 rough conically pointed ends, and more or less roughened autodermal tetracts, with 

 rounded extremities, disposed flatly in the dermal membrane (PL LIX. fig. 3). Between 

 these, pentact forms occur with uniform proximal radial rays, and sometimes diacts also 

 w^th central nodes (PL LIX. fig. 5). 



The gastral skeleton, which is not well preserved, consists of rough or spinous oxy- 

 hexacts. The pleural prostalia are simple or strongly developed oxydiacts, about 1 cm. 

 in length. 



3. Bathydorus spinosus, n. sp. (PL LIX. figs. 6-9). 



Near Penguin Island (Station 147, lat. 46° 16' S., long. 48° 27' E.), from a depth of 

 1600 fathoms and a Diatom ooze ground, the trawl brought up a thin-walled sack, 6 cm. 

 in length and 3 cm. in greatest diameter, but reduced to 2 cm. in width towards the 

 superior, irregularly contoured terminal aperture. The surface of the sack exhibited 

 irregularly scattered pointed spicules, projecting for about 6 mm., while the oscular 

 margin bears a corona of marginalia. It is possible that this sponge form does not 

 represent a distinct species, but belongs to the above described Bathydorus stellatus, 

 which it resembles in general structure, and especially in the nature of the siliceous 

 spicules. There is, however, a certain difference about to be noted, which seems to 

 warrant at least a provisional separation of the two forms. I have, therefore, regarded 

 the distinction as really specific. 



While the long diacts of the parenchymal skeleton are not in any way essentially 

 diff"erent from the long diacts of Bathydorus stellatus, I find that the abundant 

 oxyhexasters differ from those of the above species in this, that the principal rays are not 

 usually so markedly shortened, even to disappearance, as they are in the above ; the 



(ZOOL. CHALL. EXP. — PART LHI. — 1886.) Ggg 20 



