The Echinoid Directory

Key to Genera of Fibulariidae

1a.Three gonopores.

Tridium

1b.Four gonopores.

Go to 2

2a.Oral tubercles arranged bilaterally with broad, saggital naked zone.

Lenicyamidia

2b.Oral tubercles small and uniformly scattered over surface.

Go to 3

3a.Rudimentary food groove in anterior ambulacrum.

Thagastea

3b.Oral surface without a trace of a food groove.

Go to 4

4a.Periproct radially elongate; periproct covered in multiple plates, buccal membrane also plated.

Fibulariella

4b.Periproct generally circular; periproct covered by valve of 5 large plates, buccal membrane naked.

Fibularia