RHABDOCALYPTUS UNGüICULATUS. 275 



The principals are 20-25,« long as measured from the spicular 

 center, — in any case they are much longer than in E. mirabilis ; 

 they are of uneven contour and slightly swollen towards the outer 

 end (about 10/^ tliick). The terminals number 7-12 to each 

 principal and form a rather broad, lily- like tuft, expanded at the 

 outer end to a breadth of about 60/a Each single terminal is nearly 

 smooth, rather strong, thickens slightly near the distal end and 

 terminates with a small disc of a characteristic shape. This disc 

 distinctly shows some recurved marginal teeth, which are however 

 not uniformly developed, but are longest and strongest on that 

 side of the disc which is turned away from the axis of the 

 perianth-like tuft of terminals. On the opposite side of the disc, 

 I.e., the part of the disc circumference nearest the axis, the teeth 

 are smaller and often obsolete or even totally suppressed (fig. 11). 

 Thus, the disc approaches or fectually assumes e?i miniature the 

 shape of the unguiculate terminal plate in an Euplectellid flori- 

 come. The teeth, when present all around, number six, but there 

 may be only the three or four on the external side of the disc. 

 In width the disc may measure about 7/^, of which nearly 4/^ 

 constitute the length of the longest tooth. 



31icrodiscohexasters (PL XXL, fig. 9) of 22-30 />« diameter 

 are sparsely distributed in the dermal membrane. They are of 

 the usual description. 



And now a few words about the hasidictyonal plate (PI. 

 XXL, fig. 12). This consists as usual of a thin limiting plate, 

 inside of which are found some small but thick-rayed hexactins 

 in fusion with it. The uneven and irregularly cril)rate limitino- 

 plate shows roundish meshes, generally under 35 /-« in width ; its 



