Dear wofahulicodoc: that definition was the one given by the Scripps-Howard people
My dictionary gives:
echinus
n.,
pl. e[chi4ni# 73nj#8 5L < Gr echinos < IE *eDhinos, of snakes < base *eDhi3, snake6
1 SEA URCHIN
2 Archit.
a) molding under the abacus of the capital of a Doric column b) any of several similar moldings

And now, what in hell is the "abacus" of the capital? Not a calculating device for sure.

abacus
n.,
pl. ab$a[cus[es 73iz8 or ab$a[ci# 73sj#8
1 a frame with beads or balls that can be slid on wires or in slots, for doing or teaching arithmetic
2 Archit. a slab forming the uppermost part of the capital of a column

Can't fi;gure out why same name used for the two things, They sure don't look alike.
Hey, Faldage: please clear this up.