+ Central spine longer than the radials.
Radials 7 or 8: tubercles very long (40 to 50 mm.).
longimamma (36).
Radials 15 to 20: tubercles 6 to 8 mm. long.
eschanzieri (21).
++ Central spine shorter than the radials.
Radials 5 to 9, stout.
meiacanthus* (7).
Radials 9 to 22.
heyderi* (5), hemisphaericus* (6), gummiferus (8), gabbii
(34),
sphaericus (35).
*** Central spine solitary and hooked.
+ Stems slender cylindric: Lower Californian.
Centrals 1, 20 to 30 mm. long.
roseanus (23).
Centrals 1 to 4, 20 to 50 mm. long.
setispinus (24).