The Echinoid Directory

Key to the genera of Cidarinae

1a. Genital plates in females with deep brood pits.

1b. Genital plates unmodified.

Go to 2

2a. Spines with long collar, tuberculate on one side; distal part of spine with fine longitudinal striae.


2b. Spines with short collar; either smooth or ornamented.

Go to 3

3a. Primary spines with three or four prominent whorls.


3b. Primary spine without whorls.

Go to 4
4a. Primary spines with flange-like spines and ribs. Secondary spines small and scale-like.

4b. Primary spines without flanges.

Go to 5
5a. Primary spines with smooth, glabrous shaft, with only faint ribs distally.
Go to 6

5b. Primary spines with ribbed or beaded shaft.

Go to 9
6a. Ambulacra 40-50% width of interambulacra; genital plates radially elongate and widely in contact.

6b. Ambulacra about 30-35% width of interambulacra; genital plates only just in contact - not radially elongate.

Go to 7
7a. Primary spines completely devoid of cortical hairs
Go to 8
7b. Shaft of primary spines with cortical spines that coalesce to form a smooth outer layer.

8a. Granulation moderately well developed outside the scrobicular circle on interambulacral plates.

8b. Sparse granulation outside scrobicular circles on interambulacral plates.