Shape of ambulacra and pore pairs: ambs petaloid on top surface online, one pair of pores per plate, pores round and close set except when respiratory tube feet present - then may be elongated
Back
Card 18
Front
Position of anus: outside the apical system in the posterior interambulacrum - migrated to rear or bottom surface
Back
Card 19
Front
Apical system: 10 plates, arranged in 1 or 2 rings around the periproct
