262 ART. 7. 1. IJIMA : HEXACTINELLIDA, IV. 



is by no means of such frequent occurrence as one might be led 

 to suppose from F. E. Sciiulze's statement in the Challenger 

 Report. The tips are acuminate, rounded, conical or mucronate ; 

 occasionally swollen to a club-like or even a bulbous shape. 

 Sub terminally rough in varying degrees ; the microtubercles, when 

 strongly developed, are retroverted. 



The parenchymalia undergo synapticular fusion close to the 

 basal attachment and in conjunction with the basidictyonalia. In 

 certain specimens the fusion was limited to the central parts of 

 the base ; in others it extended to the external surface. 



The basididyonal plate is at places represented by a very 

 thin reticular layer quite agreeing in appearance with F. E. 

 Schulze's pi. LXIV., fig. 3, in the Challenger Keport. At 

 other places it is of a considerable thickness, being composed of 

 basidictyonal hexactins ankylosed together in the usual manner. 



The hypodermal pentactins show essentially the same char- 

 acters and arrangement as in R. victor. Paratangentials, not 

 exceeding o mm. in length ; the shaft, longer, up to 10 mm. The 

 former are more or less paratropal, but cases of their being quite 

 or nearly regularly cruciate are not infrequent. This may be 

 explained by the fact that the hypodermalia do not lie close 

 together in their groups (PI. XX., fig. 12) and consequently their 

 shafts run a certain distance apart from one another, thus depart- 

 ing in a measure from the condition that causes the paratropism 

 in a developing hypodermal pentactin. Not uncommonly four or 

 five pentactin-heads are seen in a group, of which the most 

 superficially situated {i. e., the oldest) one or two have the four 

 paratangential rays provided with the spiny armature. The spines 



