38 HOLASCELLA ANCORATA. 
these spicules are exquisitely anchor-shaped in consequence. To this the name 
refers. 
Shape and size. The single specimen (Plate 23, fig. 9) is a conic tube 40 
mm. long. It is circular in transverse section, broken off at both ends, at one 
end 11 mm. in diameter, at the other 7 mm. _ Its wall is continuous, not perfo- 
rated by parietal apertures, and about 2 mm. thick. To the narrower end a 
root-tuft appears to have been attached. 
The colour in spirit is dirty brown. 
The skeleton. The chief support of the tubular body is a paratangential 
network of principal spicules held together and in position by slender comitals. 
The principals have from three to five, rarely six rays. Two opposite rays 
extend more or less longitudinally. One or both of these longitudinal rays 
are longer than any of the others. All the rays of the triactines and tetractines 
and four rays of the pentactines and hexactines lie paratangentially; one ray of 
the pentactines and two rays of the hexactines extend radially. These radial 
rays are always shorter than the others. The comitals, which are attached to 
the rays of these principals, are diactines, triactines, and tetractines. Besides 
these spicules a few tetractine and a good many hexactine megascleres, with spined 
rays, much smaller than the principals of the supporting network, occur in the 
choanosome. Hypodermal and hypogastral hexactines, with the two (opposite) 
rays of one of the axes differentiated, occur below the dermal and the gastral 
surface. One of these differentiated rays is elongated, the other thickened and 
more or less spined. The axis of the two differentiated rays is situated radially ; 
the elongated ray points inwards, the thickened and spined ray outwards. A 
few spined anchoring spicules have been found in the narrower part of the tube. 
They are probably root-tuft spicules of the sponge. In addition to the spicules 
mentioned, rods and tetractines to hexactines with very short, stout rays, 
probably foreign to the sponge, have been observed in the spicule-preparations. 
Of microscleres spined microhexactines, floricomes, onycho- and discomicro- 
scleres, and a few main-ray crosses without end-rays have been observed. Among 
the onycho- and discomicroscleres microhexactines and hemihexasters are 
much more frequent than true hexasters. Some of the main-ray crosses observed 
are the central parts of the floricomes; others may be centres of graphiocomes. 
The discomicroscleres are very numerous and doubtlessly proper to the sponge. 
All the other microscleres are rather rare and one or the other of them may be 
foreign to the sponge. 
Among the large triactine to hexactine principal spicules (Plate 23, fig. 4; 
