REPORT ON THE HEXACTINELLIDA. 139 



circular, smooth-margined opening to the deep saccular gastral cavity. A group of 

 diact and pentact pleuralia, whose tangential rays form a kind of veil, project radially 

 from each of a number of small, regularly disposed, rounded elevations of the 

 surface. In the neighbourhood of the simple unarmed oscular wall a number of strong 

 isolated diacts project upwards. Between the dermal layer and the sieve-like gastral 

 layer which stands above it the soft parts form a deeply folded plate with alternating 

 iuhalent and exhalent radial funnel-shaped canals. 



The parenchyma contains oxyhexasters with very short main rays and various disco- 

 hexasters. The spicules of the dermal membrane are almost exclusively pentacts. 



1. Rossella antarctica, Carter (PI. LV.). 



Of the two species of Rossella hitherto known, viz., Rossella antarctica, Carter, 

 <and Rossella velata, Wyville Thomson, the former is represented in the Challenger 

 collection by numerous specimens, which vary considerably in size, and were collected at 

 four different stations. 



Several specimens, from 2 to 4 cm. in height, growing on small fragments of bivalve 

 shells and similar objects, were dredged to the south-east of Prince Edward Island 

 (Station 145, lat. 46° 43' 0" S., long. 38° 4' 30" E.), from a depth of 140 fathoms, and 

 volcanic sand ground. Numerous specimens of very various dimensions, up to 

 30 cm. in length and 15 cm. in breadth, were dredged to the south of the Kerguelen 

 Islands (Station 150, lat. 52° 4' S., long. 71° 22' E.), from a depth of 150 fathoms, and 

 a coarse gravel ground. Other forms of almost equal dimensions Avere obtained in 

 Christmas Harbour, Kerguelen, at various depths, from volcanic mud ground. All 

 these more or less well-preserved spirit specimens were attached at their base to stones, 

 either directly or by means of small processes. Finally, several specimens, attaining a 

 length of 20 cm., were trawled to the east of Buenos Ayres (Station 320, lat. 37° 17' S., 

 long. 53° 52' W.), from a depth of GOO fathoms, and a green sand ground. These also 

 were attached, either directly or by means of small processes and prolongations, to stones 

 or other solid bodies. 



The general form of this sponge may be described as barrel- or keg-like, or else 

 as resembling an elongated pear. The lower, sometimes somewhat narrowed, solid 

 end is either attached over its entire breadth to some large solid body, or is 

 fastened by short lateral processes of irregular form to various smaller objects. I have 

 never found the peculiar loose root-tuft which Carter represents in his diagrammatic 

 figure ; ' but I have noticed such a structure on one of the two original specimens 

 preserved in the British Museum, and it is quite possible that this modification, as 



' A nn. and Mag. Nat. Hist., ser. 4, vol. xv. pi. x. fig. 4. 



