29 



peristome, the series of primary luberdes not ending so abruptly close below the 

 ambitus. There are eight longitudinal series of larger tubercles in each inlerambu- 

 lacrum at the ambitus in both specimens; in graniilatuni specimens of a correspon- 

 ding size have ten series at the ambitus. The tubercles are somewhat smaller than 

 in gramilatiim , the tuberculation being upon the whole much scarcer than in that 

 species. The longitudinal series are parallel to the median line of the area. The 

 granulation of the inner part is much less close than in gramilatiim, and the limits 

 of the plates are distinct (especially in the specimen figured from the abactinal 

 side; unfortunately, the actinal side was so badly preserved in this specimen that 

 it could not be figured). 



The pores are very distinct along the whole actinal side, and are nearer to- 

 gether and much larger than in granulatiim ; they are not crowded at the ambitus. The 

 spines are like those oï gramilatiim, wilh oblique basis; those of the actinal side are 

 rather coarse and not so close set, the bearded appearance being 

 not very noticeable. The colour as in granulatiim, excepting the 

 arrangement of the blue spots. — The pedicellariæ are mainly like 

 those of gramilatiim; the tridenlate pedicellariæ, however, differ 

 somewhat in form. They are shorter (c. 1 mm., head), often four- 

 valved ; the valves (Fig. 2) are not widened at the point, the edge 

 of the lower part is bent outwards, and coarsely serrate; the smaller 

 forms are like those of gramilatiim. The claviform pedicellariæ 

 may have the head developed, the valves being similar to those 

 of gramilatiim only more slender (Figure can not be given, as I 

 have no good preparation of them). — The spicules are arranged 

 more or less distinctly in four longitudinal series; they are Iri- 

 radiate, slender, but more irregular than in gramilatiim. In the 

 abactinal tubefeet similar spicules may be found at the tip. 



Through this new species of Chœtodiadema it becomes 

 evident, that the very close granulation of the actinal side is 

 not the essential character of this genus, this feature being much 

 less developed in Ch. japoniciim than in granulatiim. The main 

 character of Chœtodiadema is: the arrangement of the pores in a tridenlate pedicellaria 

 single series on the actinal side, by which feature it is at once "f Chœiodiadema 

 distinguished from Astropyga , to which genus it has otherwise a 

 great resemblance. Quite small specimens of Astropyga certainly 

 will show the same character; this cannot, however, alter the value of the genus 

 Cha'todiadema. The occurence of a primary tubercle on all the ambulacral plates 

 is no exclusive character of the genus, being found also in A. denudata, which 

 species upon the whole seems to stand rather near Chœtodiadema. 



lig. 2 \ alve of 



japunknni, (Seib. 

 Obj. II. Oc III. 



