xl THE VOYAGE OF H.M.S. CHALLENGER. 
a. Abactinal skeleton tessellate, arranged in more or less regular lon- 
gitudinal series. With intra- and infra-marginal papule. 
Primary apical plates persistent in the adult. Marginal plates 
well developed and always contingent. 
a. Superambulacral plates usually present. Tegumentary develop- 
ments granulate. Pedicellarie (rarely present) ex- 
cavate 3 ¢ Q : 5 : 3 5 
6. No superambulacral plates. Tegumentary developments spi- 
nulate. Pedicellariz (forcipulate) pedunculate, 
a, Adambulacral plates unequal, alternate plates with promi- 
nent ridges. Adambulacral armature complex, poly- 
acanthid. Pedicellariz (forcipulate) pedunculate . 
f. Adambulacral plates small, equal, compressed, with no 
ridges. Adambulacral armature simple, diplacan- 
thid. Pedicellariw forcipiform and forficiform 
b. Abactinal skeleton reticulate, more or less irregular. With ‘or 
without intra- and infra-marginal papule. Primary apical 
plates aborted in the adult. Marginal plates feebly developed 
and often separated by intermediate plates. 
a. With no intra-marginal papule. Adambulacral armature pec- 
tinate. Abactinal skeleton with a more or less highly 
developed composite spinulation (subpaxilliform). 
a. With actinal intermediate plates more or less developed. 
Interbrachial septa present. No supradorsal mem- 
brane é c 5 - : ; : 
B. No actinal intermediate plates. No interbrachial septa. 
With a supradorsal membrane forming a more or 
less perfect nidamental cavity . ; ¢ : 
b, With intra-marginal papule. Adambulacral armature isolate 
or grouped, not pectinate. Abactinal skeleton with 
spinelets isolated or grouped, but never composite or 
paxilliform. 
#, With double interbrachial septa 
8. With single interbrachial septa. 
i, Actinostomial ring with adambulacral plates promi- 
nent. Ambulacral tube-feet biserial. 
1. Pedicellarie rarely present, never forcipiform. 
Abactinal skeleton forming an irregular 
meshwork : - : . 
2. With forcipiform pedicellarie. Abactinal skele- 
ton forming a regular quadrangular mesh- 
work : c 2 : c : 
ii, Actinostomial ring with ambulacral plates promi- 
nent. Ambulacral tube-feet quadriserial 
B. Marginal plates in part aborted altogether, elsewhere represented only 
by microscopic rudiments. Abactinal skeleton aborted, or present 
only on the disk and ovarial regions. Parambulacral and inter- 
mediate actinal plates altogether absent. No interbrachial septa. 
Spinelets in sheaths clothed with pedicellariz 
Linckp2. 
ZOROASTERIDE. 
STICHASTERID&. 
SOLASTERID&, 
PTERASTERIDE. 
HELIASTERIDZ. 
EcHINASTERIDS. 
PEDICELLASTERIDE. 
ASTERIIDE. 
BRISINGID2. 
