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; 



