R. PHŒNIX. SPICULATION. 271 



and tlie lateral wall, the parenchymalia are chiefly cliactins with 

 an occasional sprinkling of slender thetactins and of similar 

 hexactins which have one axis greatly elongated in excess over 

 the others. 



While the thinner parenchymal strands consist solely of the 

 thin filamentons spicules, the coarser ones contain large bow- 

 shaped or boomerang-like oxydiactins, the principalia, in addition 

 to the much more slender comitalia. The principalia may 

 measure 50 mm. or more in length and 290/^ in thickness at the 

 middle which is smooth and either gently curved or bent in an 

 elbow-like manner. The finely attenuated ends are smooth-sur- 

 faced. In forming a bundle, the principalia are arranged side 

 by side and one after another in overlapping series, each sur- 

 rounded by a copious quantity of the comitalia. 



The comitalia and all other fine parenchymal diactius are 

 either annulated or cruciately knobbed at the center ; their ends 

 rounded or conically pointed, often swollen and subterminally 

 roughened to a greater or less degree. 



The radial beams of the sieve-plate, which are to be con- 

 sidered as outward continuations of the parenchymal bundles, are 

 supported by certain prolonged rays of large, unequally rayed oxy- 

 pentactins (occasionally oxystauractins) arranged in a circle along 

 the sieve-plate border. (PI. XT, figs. 5, 6). Similar spicules in 

 the same position and arrangement have been described by 

 F. E. Schulze in Dictyaulus elegans, and by myself in R. home- 

 yamai (see p. 259). The plane of the two corap)lete and 

 cruciately disposed axes is concave on the inner side, and on this 

 side the sixth atrophied ray is always represented by a small, 

 conical protuberance. The outwardly directed, unpaired ray is 



