A. JBJ. Verrill — Revision Geyiera and Species of Starfishes. 219 



Sideriaster Ver., gen. uov. 



Form broadly stellate with a very large disk ; dorsal surface con- 

 vex, and capable of inflation, closely covered with uniform, stellate 

 paxillse. Upper marginal plates small, entirely lateral. 



Interradial actinal areas are large, with numerous plates, the distal 

 ones extending to the distal third of the rays. They are arranged in 

 single radial series, each series usually corresponding to an adam- 

 bulacral plate and most of them to a marginal plate, but some of the 

 series are short and do not reach the margin, there being more 

 adambulacral than marginal plates proximally, but distally they 

 generally correspond in number, though there are sometimes, locally, 

 two marginals to one adambulacral. These plates are covered with 

 granules, and have divergent, fasciolated spinules along their radial 

 margins, thus forming fasciolated grooves that are coincident with 

 those between the marginal plates. 



The abactinal paxillae are large, closely arranged, and nearly 

 uniform in size and shape, regularly stellate, with short, even 

 sj^inules. 



The madreporic plate is very large, round, flat, fully exposed, and 

 has very numerous, thin, radiating gyri. 



Papular pores are very numerous and are arranged singly, about 

 six around each plate over the whole of the disk and rays, even close 

 to the ends. 



There is no distinct dorsal nephridial pore visible, nor do the cen- 

 tral plates differ in size from those of the disk in general. 



Marginal plates are small and not prominent. The upper ones 

 are entirely confined to the margin, and are granulated, without 

 spines. The lower ones form the lower part of the margin, but 

 extend also on the disk below ; they are spinules with a median row 

 of larger spines. 



The adambulacral plates have a prominent furrow angle, on which 

 there is a large, median, odd compressed spine ; at each side of this 

 there are, in the furrow-series, two or three erect flattened spines ; 

 a stout spine occurs on the center of the actinal side, with a single 

 or double row of shorter flat spines back of it. 



The jaws are large, not very prominent, covered with numerous 

 short, blunt spinules and having furrow spinules like those of the 

 adambulacral plates. 



This remarkable genus seems to be very distinct from all known 

 forms, but clearly belongs to the Astropectinida. Its very broad 

 cnnvex disk and large actinal interradial areas and small marginal 

 plates are exceptional ; and so is the very large madreporic plate. 



