250 K. MITSUKUEI : STUDIES ON 



shown in textfig. 50 a. Like so many other species of Cucumar'm, 

 the ventral median radius and its two adjoining interradii are fused 

 into a large three-pointed piece. Posterior prolongations present on 

 the radii, none on the interradii. Retractors divided at about 

 the middle of the body -length. 



Calcareous deposits : — Nearly all are tables with imperfect 

 spire (c). The disk is more or less lozenge -shaped ; with four, 

 easily distinguishable, principal holes, in additon to which there is 

 a larger or smaller number of accessory lioles. The whole looks 

 rather delicate. All have smooth margins. Occasionally there 

 occur unusually large ones (c). These disks are each provided 

 with an imperfect spire. This is often represented by nothing 

 more than two knobs situated in longitudinal line ; but it is as often 

 built into an irregular spire, generally with only two columns. These 

 spicules are evenly spread in the perisomo, so that they can not 

 be described as being crowded or heaped up in layers. In the 

 pedicels, spicules are modified into supporting rods, becoming 

 much elongated transversely (d) ; in the enlarged middle of the 

 biscuit- shaped disk there are the four principal holes, over which 

 is built a more or less imperfect spire. Both ends are also sHghtly 

 enlarged with one or more holes. In the wall of the pharyngeal 

 mass, there are spicuk'S wdiich are similar to those in the perisome, 

 but are larger and have serrated margins {h). In the tentacles, 

 again, there are similar spicules in the branches ; but on the stem, 

 they become modified into supporting rods of a much elongated 

 shape. These have, besides the four principal holes in the enlarged 

 middle, a series of other holes extending into each arm and some- 

 times showing an increase in their number and width towards 

 both ends. 



Remarhs : — This seems to be a well marked species, and yet 



