CATALOGUE OF ECHINIDA. 
Synopsis of the Genera. 
I Pores of each amhjlacral band united by a cross groove. 
A. Infra-arnbulacral grooves, simple , straight, not branched. 
a. Ambulacral petals broad, closed at end. 
1. Clypeaster, under-side concave. 
b. Ambulacral petals narrow, open at end. 
2. Laganum, vent inferior ; body pentagonal. 
3. Arachnoides, vent supra-marginal ; body circular. 
B. Infra-arnbulacral grooves branched near end, or waved ; vent 
inferior. 
c. Ambulacral petal narrow, open at the end. 
4 . Echinarachnius, discoidal entire ; vent sub-marginal ; oral 
grooves just branched at the end. 
5. Dendraster, discoidal entire; vent sub-marginal; oral 
grooves much branched. 
6. Rotula, discoidal pierced, and lobed ; vent sub-oral. 
7 . Leodia, discoidal pierced ; edge entire ; vent sub -oral. 
d. Ambulacral petals broad, closed at the end. 
8. Echinodiscus, discoidal pierced ; vent sub-marginal ; . oral 
grooves round or slightly branched. 
9. Mellita, discoidal pierced ; vent sub-oral ; oral grooves 
waved. 
10. Echinoglycus, discoidal pierced ; vent sub-oral ; oral 
grooves much branched. 
11. Pores of each ambulacral band not united by a cross groove. 
11. Moulinsia, discorded, edge festooned. 
12. Echinocyamus, oblong, edge rounded. 
13. Fibularia, sub-spherical. 
I. Pores of each ambulacral band united in pairs by a cross 
groove ; cavity of the shell strengthened internally, at least on 
the margin. 
A. Infra-amhulacral groove, simple, straight, not branched, 
a. Ambulacral petals broad, closed at the end. 
1. Clypeaster. 
Shell pentagonal, truncated behind, beaked in front, swollen, 
sometimes conic, or sub-conic ; beneath flat ; ambulacral petals 
very broad, sometimes costulated, arched, and circumscribed 
by very broad periferous zones, corresponding with five narrow 
