228 
THE VOYAGE OF H.M.S. CHALLENGER. 
6. Suhcortical spheraster, an evident centrum and numerous rod-like actines, 0’016 
min. in diametor. 
7. Choanosomal chiaster (PL XXVI. fig. 9), no visible centrum, somewhat, but not 
very numerous, slender, hair-like or rod-like actines, from O'OllS to 0'016 mm. long; 
total diameter 0'024 to 0'0276 mm. 
Colour. — In the dried state nut-brown. 
Habitat. — Station 122b, off Brazil, September 10, 1873 ; lat. 9° 9' S., long. 
34° 53' W. ; depth, 32 fathoms ; bottom, red mud. Trawled. 
Remarks. — The species is represented by a single specimen, the largest Tetractinellid 
sponge known. The cup stands on a rounded base about 12 cm. in diameter, and rises 
to a height of 40 cm. At its broadest part its diameters are 22 and 31 cm. The in- 
terior conical or funnel-shaped cavity commences about 12 to 13 cm. from the base. In 
the illustration it is represented as extending completely through the basal part of the 
sponge ; this is the result of an injury, or to the sponge having grown over some stake- 
like support which has since been torn away. The actual extent of the true internal cavity 
is indicated in the figure (PI. XXV.) by the broad white line which represents the cortical 
layer of the interior ; this will be observed to suddenly cease at the point where the basal 
perforation begins. The diameters of the cup at its margin are 21 and 15 cm. Thin at 
the margin, the walls increase in thickness downwards, and 12 to 13 cm. from the summit 
they measure 45 mm. where thinnest and 85 mm. where thickest. Both inner and outer 
surfaces are. much folded, growing out into irregular, sinuous, branching, anastomosing 
ridges, diversified by lobes and tubercles. On the outer surface the ridges in their up- 
ward growth frequently terminate in lobate summits ; and the irregular grooves between 
them are frequently circumscribed, forming pits, which descend deeply into the thickness 
of the sponge-wall, as sinuous cavities. The mouths of these canals are shown in PI. 
XXIV. The upper half of the interior surface (PI. XXV.) is folded into sinuous, more or 
less longitudinal, ridges, which as they descend become confluent in an irregularly undu- 
lating surface. Looking at the margin of the cup, face on, it is seen to be irregularly 
plicated or “ goffered.” The margin may be regarded as the latest formed part of the 
sponge, and from its manner of growth we obtain a key to the complications of the older 
and indeed aged part of the sponge-wall. Let us assume that at an early stage the young 
sponge acquired a cup-like form. The mode of growth of the margin was similar to that 
of the existing margin ; i.e., the growth of the surface proceeded more rapidly than 
that of the interior of the wall, and folding of the margin was the result (Fig. 2, a). 
The pleats once formed continued to grow in the same manner, i.e., the superficial growth 
was more rapid than the deep-seated, and secondary and tertiary pleats arose upon 
those first formed (Fig. 2, h, c), more particularly on those of the exterior of the sponge- 
wall. It is well known that concrescence frequently results when two growing surfaces 
