264 I. IJIMA : HEXACTINELLIDA. I. 



200 n in diameter. The principal is about 10 n long, as measured 

 from the axial center. The terminal sheaf is 12 /' thick, keeping 

 nearly the same width throughout or only slightly oxpnuding 

 toward tlic outer end. 



The oni/ehmfers (PI. X, fig. 12) occur in abundance every- 

 where in the parenchyma. They are 80-t>(') n in diameter, i. e., 

 about as large as in i?. phoenix but of more uniform size. From 

 each short principal (0 « long as measured from the axial center) 

 there arise 3-o, thin, tapering, nearly straight and strongly diver- 

 gent terminals. The finely attenuated end of these bears a whorl 

 of ;> or A, fine minute claws of just the same appearance as those 

 to be described under R. phcenix (PL X, figs. 20, 21). In some 

 onychasters, tlie terminals and the claws were found to be less 

 fine than in others. 



Finally, the rigid basal mass is composed of an irregular frame- 

 work of siliceous beams (PI. X, fig. 17). These are 20-35 /^ thick ; 

 smooth but witli occasional microtubercles or prickles. The 

 inclosed meshes are, though not alwaj's, rather wide (measuring 

 ui> to 200 ri or more across). The framework is formed by 

 synapticuhir fusion of not only diactin-parenchymalia but also 

 of certiiiu thick-rayed hexactins, tiie hasidictyonalia, observed in 

 so many other Lyssacina with liaid i)ases (p. 232). This is proved 

 by the presence of the hexradiate axial cross in the beams and 

 also by such hasidictyonalia in different stages of amalgamation 

 as still retain their original external form. 



