6 



S. YOSHIWAKA. 



in a very slight degree. Close to the periproct again, the overlapping 

 just referred to is not recognizable. 



Apical system (fig. 5) star-shaped, not projecting, the plates lying 

 partly in apposition, partly separated by more or less wide membranous 

 interspaces. The larger and peripherally situated apical plates with 

 tubercles for psdicellariae and secondary spines. Basais (bas.) wedged 

 into interambulacrum and bearing a short membranous tube with 

 genital opening (g. o.). Eadials [rad.) ssparated from basais, usually 

 with a periproctal {per.) between. Anals (an.) very small, elongated, 

 closely packed together. Anus somewhat projecting. 



Ambulacrum straight, narrower than interambulacrum (the ratio of 

 breadths of the two being 28 to 41 at ambitus). 



Ambulacral plate is composed, as determined near ambitus, of an 

 aboral section and of a small, narrow, imperfectly calcified, adorai section 

 situated at the middle of lower edge (fig. C, am.). Closer -observation 

 shows that the former again consists of three pieces apposed together in 

 a transverse row. A pair of pores is situated on the outermost piece of 

 the aboral.section. This pair of pores, together with two more pairs 

 found side by side on the adorai section, forms a tolerably broad pori- 

 ferous zone. — Towards the periproct the divisional lines between the 

 pieces making up the aboral section become more and more difficult to 

 distinguish and towards the periproct the adorai section apparently loses 

 one of its pairs of pores, so that there now remain only two pairs of 

 pores to each ambulacral (fig. 5, am.). Finally the adorai section 

 itself is no longer recognizable a,s such and henceforth the row is 

 continued to the periproct by a few. very imperfectly calcified plates, 

 each with a single pair of pores. 



Peristomal ambulacrum consists of transversely narrow plates, each 

 with a single pair of pores. They are arranged in each peristomal ambu- 

 lacrum in two regular rows reaching the mouth, between which are 

 irregularly interposed a few other plates eonfined to the peristomal 

 periphery. The pairs of pores on the two rows form a continuation of 

 the outermost series of those of the coronal ambulacrum. Those of 



