from Japan and the Indian Ocean. 83 



The interambulacral areas are twice as broad as the ambu- 

 lacral. On the actinal side there is a rather regular series 

 of large tubercles along the outer edge of the area and 

 another more irregular seiies along the median part of the 

 plates. A large intermediate tubercle is found on the plates 

 near the ambitus, and on all tiie plates except a few of the 

 adoral ones there are some medium-sized tubercles, forming 

 an indistinct horizontal row on each plate. Several small 

 tubercles are placed between the larger ones; they may be 

 arranged along the inner and outer edge of the plates, but 

 mostly they are irregularly distributed. The scrobicular areas 

 are rather deep, provided along the edge with a circle of smalF 

 depressions, a feature not known to me in any other Echino- 

 thurid. The membranous interstices (the sutures) between 

 the plates are rather large ; they can be seen only when the 

 epidermis has been removed; they are directed a little 

 adorally at the inner and outer end (PI. II. fig. 1). The 

 extension of the lapping of the plates is visible only from 

 the inside of the test, so that, not having opened any of the 

 specimens, I. cannot give any particulars. On the abactinal 

 side the tubercles are few, smaller, and quite irregularly 

 placed. The sutures between the plates rise obliquely from 

 the median line of the area. 



In the ambulacral areas there is, on the actinal side, a large 

 tubercle on the inner half of the large component, but only on 

 every second plate, or even more distant ; these tubercles do 

 not form a very regular longitudinal series. Some smaller 

 tubercles are placed irregularly on the ambulacral plates, at 

 the inner edge or in the outer part, between the pores. The 

 edges of the plates irregular, the plates widening where the 

 large tubercles are placed. On the abactinal side the 

 tubercles are very few and small, irregularly placed. The 

 pores are very conspicuous, forming three rather distinct 

 longitudinal series. Towards the apical area they are more 

 irregularly placed, forming sometimes arcs of four, and it can 

 scarcely be doubted that some of these plates have really four 

 pairs of pores — a fact of no small interest, indicating that also 

 in the family Echinothuridge multigeminate pores may occur 

 (comp. Felanechi'nus). 



The plates of the actinostome do not present peculiar 

 features. 



The primary spines of the abactinal side are evidently 

 rather variable in length ; in one of the specimens from 

 Hamburg they are more than 25 mm. long (I have seen none 

 unbroken), in the specimen figured they are more slender 

 and have evidently been shorter; thev are smooth and 



G* 



