JAPANESE ASÏEROIDEA. 181 



spines, the number of wliich may vary from as few as three or four 

 up to as many as nine or ten. When there are only three or four, 

 it frequently happens that two or three of these spines stand close 

 together on the outer part of the plate, and one somewhat apart 

 on the inner part. When they are more numerous, however, they 

 usually form a continuous series, leaving only the outermost part 

 of the plate free, as represented in fig. 76. It may also be added 

 that the individual spines are larger when there are fewer than 

 when they are more numerous. 



The series of conspicuous spines above described divides, in 

 a general way, the surface of a superomarginal into two portions 

 wliicli show a difference in their armature. In the abcentral part 



ft 



of each superomarginal the armature consists of very small, thickly 

 set, cylindrical spinelets, while in the adcentral portion, which is 

 the larger one, the armature immediately contiguous to the series 

 of conspicuous spines may best be described as scaly, and the 

 scaly form gradua 11}^ passes on to a cylindrical towards the margin. 

 On the outer face of the plate the conico -cylindrical spinelets are 

 somewhat better spaced. The fasciolar grooves are thickly covered 

 with capillary spinelets. It must finally be remarked that in 

 the interbrachial angles the conspicuous spines are less numerous. 



At the interbrachial angles the superomarginals are higher 

 than broad, but nearly half as high as broad at the middle of the 

 arms, where they are also half as long as broad. On the outer 

 side the superomarginal plates are perfectly rounded, so that we 

 can not well speak of an external edge. The number of supero- 

 marginals is given in the foregoing table. 



Inferomarginals. — The inferomarginnls are much broader than 

 long, and bear each a transverse series of spines, which are very 



