Yerrill, Notes on Radiata. SVS 



bearing a large, smooth spine. luteranibnlacral plates bearing a row 

 of smaller, inner sjnnes, several on each plate, and an outer series of 

 larger ones, one to each plate. 



This genus is nearly allied to Oreaster, and still more so to JVido- 

 rellia. From the former it differs in its depressed form, tessellated, 

 polygonal plates, the character of the spines, etc. ; from the latter, in 

 tlie larger and less numerous plates of the up})er surface, consisting 

 mainly of the three median rows of the rays, with very few in the 

 interradial regions, while in Nidorellia they are nuich more mimerous 

 and the interi'adial regions of the upper suiface are well developed. 

 The marginal plates, also, in the single known species, are granulated 

 only around the margin. 



Amphiaster insignis Verriii, sp. nov. 



Plate IV, figure 1 0. 



Proportion of the radii of rays to those of the disk, nearly as 2:1. 

 Rays broad at base, small, but not acute, at the tips, with the interra- 

 dial margin deeply and regularly incurved in young specimens, slightly 

 angular in larger ones. Along the upper side of the rays, there are 

 three rows of regular plates, which are rather large and somewhat 

 prominent, and each normally beax's a large, sharp, conical spine, 

 smooth above, but surrounded by granules at the base. These spines 

 form, therefore, three regular rows on the rays, except near the tips, 

 where the lateral ones become obsolete. The spines increase in size 

 toward the center. The five inner ones of the median rows are often 

 absent, the corresponding plates presenting a smooth, rounded sur- 

 face, as if the spines had been broken oft' and the scars had healed 

 over ; frequently, also, several of the other median spines are wanting 

 in the same way ; but the number and positions of the naked plates 

 ditter on the different rays of the same individual, and on difterent 

 specimens. In each angle between the inner ends of the median rows, 

 and terminating the lateral ones, there is a larger spine, forming the 

 angles of a pentagonal area, enclosing from three to five similar spines. 

 The large madreporic plate is outside this area, close to the base of one 

 of the spines. In the interradial regions, and surrounding the ovarial 

 openings, there are about five small plates, one or two of which often 

 bear spines in the larger specimens. The margin is rounded, and 

 formed by botli the upper and lower series of plates, those of each 

 row alternately approaching and receding from the margin. These 

 plates are variable in size, those of the upper series much the largest, 

 somewhat rounded, and in the intervals between those that are S('])a- 

 rated there are often small accessory }>lates, and at tlie angle there is 



