****** Central spines more than one, and more then one of them
hooked.
Radials 8 to 12.
wrightii* (15).
Radials 30 to 60.
tetrancistrus (22).
II. Tubercles with a more or less prominent groove.
* Central spines none.
+ Radials whitish and rigid, oppressed (pectinate) and
interwoven with adjacent clusters.
Depressed-globose and simple.
compactus (44).
Globose and simple.
radians* (45), corniferus (47).
Cespitose.
pectenoides (46), sulcatus* (49).
++ Radials more slender and spreading.