379 
-~ + + + Central spines 5 to 8. 
Radials 6 to 10: centrals annulate. 
cornigerus (13). 
Radials 12 to 14: centrals annulate. 
hamatocanthus (19). 
Radials 20: no annulate spines. 
polyancistrus (24). 
** None of the spines hooked. 
+ Central spines none. 
Ribs 8 to 10, broad. 
horizonthalonius (5). 
Ribs 40 to 55, very thin and wavy. 
phylacanthus (33). 
+ + Central spines solitary. 
Radials 5 to 9. 
Ribs 8 to 10, broad. 
horizonthalonius (5), ingens (6). 
Ribs 13 to 21. 
texensis (4), emoryi (11), rectispinus (12), 
Ribs 40, very thin and wavy. 
lancifer (34). 
Radials 14 to 22. 
Ribs 13. 
selispinus (31). 
Ribs 21. 
erectocentrus (47). 
Ribs 36 to 40. 
spinosus (35), 
++ + Central spines 2 or 3, 
Radials none: ribs 10 to 15. 
major (36). 
Radials 8: ribs 8. 
papyracanthus (49), 
Radials 11 to 18: ribs 13. 
sileri (48). 
Radials 14 to 16: ribs 18. 
setispinus (31). 
++ + + Central spines 4. 
Ribs 8. 
Radials 8 to 10. 
hystrichacanthus (37), bicolor (38), papyracanthus (49). 
Radials 11 to 17. 
bicolor (88), schottii (39). 
Ribs 18 to 21. 
Spines all rigid and annulate. 
polycephalus (1), reranthemoides (2), parryi (3), viridescens (8). 
At least some of the radials setaceous or bristly. 
lecontei (15), jonesii (16). 
Spines dissimilar (one or more flattened). 
orcuttit (40), limitus (41). 
Spines similar (all flat or all terete), closely interwoven. 
johnsoni (42), intertextus (45), dasyacanthus (46). 
Ribs 36 to 40. 
spinosus (35). 
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