Mr. H. J. Carter on the Genus Rossella. Ay 
arm 32 by 1-6000th of an inch in its greatest diameters, that 
of the inflation and rays about 73-6000ths of an inch long 
(N.B. This is the characteristic rosette of the species). Size 
of entire specimen 1?inch long by 10-12ths of an inch broad, 
and 74-12ths of an inch thick; aperture about 74-12ths of 
an inch long by 2-12ths wide; margin thick, round; depth of 
cavity 14 inch; thickness of wall about 3-12ths of an inch. 
Hab, Ocean-bed. 
Loc. Antarctic Sea in 300 fathoms, and lat. 744° 8S. 
Obs. The hexactinellid character of the spicules of this 
sponge, together with the free termination of the “ anchoring- 
spicule’ in four stout spines or hooks recurved and opposite 
(PI. X. fig. 3), characterizes the genus, viz. that of ‘“Rossella;”’ 
while the erect beard of spicules round the aperture (fig. 4, c), 
and the peculiar form of the flesh-spicule (no. 10, fig. 6), which 
is by far the most abundant, determine the species, viz. 2. ant- 
arctica. ‘There is no rosette-like flesh-spicule that I have yet 
seen wherein the arms are so distinctly, although so sparsely, 
spined, and the rays so parallel, so little divergent at their 
extremities, and so little inflated or capitate. (Altogether, 
the slightly inflated end of the arm, and the microspined rays 
which it supports, are a miniature form of the head of the 
scopiform spicule of Aphrocallistes beatrix, ‘Annals,’ 1873, 
vol. xu. pl. xv. fig. 2.) It is not improbable that there are 
other forms of the rosette flesh-spicule present in this species 
besides those described; but if so, I have not seen them, 
and if there are any, they are of no consequence in a specific 
point of view after no. 10. 
ft. antarctica further differs from the two following species, 
so far as my observations extend, in not possessing the other 
flesh-spicules or forms of rosette which are common to both 
Rh. velata and R. philippensis; while it agrees with R. velata 
in the more or less developed state of all the arms of the sex- 
radiate spicule of the latticework layer on the surface, thus 
differing from R. philippensis, in which for the most part the 
four horizontal arms alone are present. 
I have described the monticular and latticework layer of 
the surface in a much more perfect state than it exists in the 
specimens of 2. antarctica to which I have alluded, where, 
from rough usage at some time or other, as im some of the 
specimens of £. philippensis, a great part of the latticework 
layer has been ‘abraded, thus rendering the cribellate and 
monticular surface below more evident; but still enough of 
the former remains here and there to show what the specimen 
was in its entirety. 
From the presence of several minute specimens of this 
