90 PTERASTERIDAE. 
B.. No true suboral spines though the innermost of the 3 orals might be so considered......... trias. 
BB.! Suboral spines present. 
C2 No small marginal spines on oral plates. 
D2. 3 large, subequal spines on each oral plate (all suborals or 2 suborals + loral)....... edazx. 
DD. 2 large spines on each oral plate (both suborals or 1 suboral + 1 oral). 
Et. Valves of osculum with 5 or 6 spines; paxillae with 5-8 spinelets; color yellowish white. 
campanulatus. 
EE. Valves of osculum with 10 spines; paxillae with 4 spinelets; color dark or at least dusky. 
purpureus. 
CC2 Marginal spines (orals), smaller than suborals, present on oral plates. 
D.* Suboral spine single. 
E2 Adambulacral spines 2; membranes fleshy; spiracula very small and grouped; orals 4-6. 
F. Suboral spine like a segmental papilla.............-...-.----- -+---- pentagonalis. 
FF. Suboral spine not like a segmental papilla.............-..---.---+------- carnosus. 
EE2 Adambulacral spines more than 2. 
F.! Rays attenuate, R = about 2r; adambulacral spines 3........-....... geometricus. 
FF.) Rays not at all attenuate. 
G. Orals 3, stout; third or fourth actinolateral spine longest............ coccinatus. 
GG. Orals 4 or 5, slender. 
H. Fifth or sixth actinolateral spine longest; adambulacral spines 3 or 4, not in a 
continuous) series... 0.6 55d Fasck cee Been eee ee eee modestus. 
HH. Seventh to eleventh actinolateral spines longest; adambulacral spines 4 or 5 in a 
CONLIMUOUS SELICS!. ..<.c.c occ es leis ein ee Sree te teee een net One quadrispinosus. 
DD.* More than one suboral to a plate. 
E.° Suboral spines 2 on each plate. 
F2 Only 2 adambulacral spines (3 on some plates, in perissonotus). 
G2 Only 2 orals... 2.0... eect eee esndece 2 22] eee eee ene eee giboryi. 
GG. 3 or more orals. 
H.: Paxillar spinelets few, rarely more than 5, often 3. 
I. Orals 3. 
J. Actinolateral spines rather short, robust, eighth or ninth longest. . . echinulatus. 
JJ. Actinolateral spines very long, twentieth to twenty-second longest. 
giganteus. 
II. Orals 4~7. 
J. Of actinolateral spines, fifth to twelfth longest. 
K. More or less pentagonal; paxillar spinelets 4 or 5; orals4......... TOseus. 
KK. More or less stellate; paxillar spinelets usually 3; orals5........ agassizii. 
JJ.1 Of actinolateral spines, twelfth to twenty-first longest. 
K.! Of actinolateral spines, twentieth or twenty-first longest...... sacculatus. 
KK. Of actinolateral spines, eighteenth or earlier longest. 
L. Paxillar areas of rays conspicuously elevated; actinolateral spines short, 
StOUE 20. a,c cans sos OS ans ole os eo ae Eee ae eee glaucus 
LL. Paxillar areas not conspicuously elevated; actinolateral spines long, 
slender. 
M. Paxillar spinelets 3 or 4; on some plates, 3 adambulacral spines. 
perissonotus. 
MM. Paxillar spinelets 4-6; only 2 adambulacral spines........ vicarius. 
HH. Paxillar spinelets many, 5-12. 
I! Paxillar spinelets 5-7............ 30s bbl te ee Oe pellucidus. 
II! Paxillar spinelets 8-12. 
J? Form pentagonal... 2.225% 34.2.0 02%. 02-2 eee a eee perspicuus. 
JJ? Formistellate. .2cios% 6 00 sj. 5 «ieiec sot ee eee infernalis. 
FF? More than 2 adambulacral spines, except on individual plates or near tip of ray. 
G2 Color deep purple, with fibrous bands in supradorsal membrane and tips of tube- 
feet, white; adambulacral spines 3, short, thick subequal............- pullatus. 
GG Not as above. 
H? Orals 2; paxillar spinelets 5-7; adambulcral spinelets 3-5; fifth actinolateral 
spine longest .\./..<.<:.) ace cee «os foe con cies See eee praecoquis. 
* Sladen’s figure shows 4 oral spines but in his description he distinctly says there are only two. 
