EASTERN TROPICAL PACIFIC ASTEROIDEA. 89 
says, that the innermost oral should be considered a suboral but I have not the 
material to determine the point. In using the following key to the species of 
Hymenaster, these possible variations in number of adambulacral, oral, and 
suboral spines must be kept in mind and when there is any doubt both alterna- 
tives should be followed out. The key includes not only all the species listed 
above, but also the two new forms described below, each of which has some 
very distinctive characters. Of course the accumulation of more material will 
bring out defects in the present key, but it will serve as a beginning for a satis- 
factory brief expression of the taxonomy of the genus. It will be noticed that 
some of the characters which were considered of primary importance by Sladen, 
such as the reticulation of the supradorsal membrane, and the body-form, are 
here either ignored entirely or relegated to a very subordinate position. This 
has been done because these characters vary so much with the condition of the 
specimen, as to be of doubtful value. Most Hymenasters are secured only by 
dredging or trawling in very deep water and they reach the surface in a more 
or less contracted, contorted, and often damaged condition. It is therefore 
often impossible to determine what the form and appearance in life were. Since 
the caleareous parts are less likely to be altered by capture and preservation, 
I have sought to use these as far as possible in distinguishing the species. Proba- 
bly this leads to a more artificial arrangement than if all the characters could be 
considered but under existing conditions any arrangement of the species of so 
little-known a genus must be more or less non-phylogenetic. 
Key to the species of Hymenaster. 
A. Adambulacral armature of one spine. 
B. Suboral spine single. 
(Ce Oil Fakes", scodaceoberosaecudocooop hus soccucoduuccuR. aruoe EOS Umenons cremnodes. 
CC. Oral spines 3 or 4. 
D. Spiracula not in definite circumscribed areas, except for regular transverse bands on inter- 
brachial membrane; oral spines nearly as long as jaws...............+.+.-.- nobilis. 
DD. Spiracula in definite circumscribed areas but transverse bands on interbrachial membrane 
replaced by small, detached, scattered areas; oral spines about half as long as jaw or 
MOBS). Whtarcyal cy snenecrctart te eel ertens A Rd OCC COTO OR Oe aC OO nec Aap So. rra eto koehleri. 
BB. Suboral spines 2 on each plate. 
GENO pie ook vodd obuorcc tc: cob coaeduu ev cone. coOcoUad SUSnepednuanl cour formosus. 
CC. Oral spines 3 or 4. 
D.! Actinolateral membrane thin with very long actinolateral spines; spiracula very small 
in widely, scatteredsexOups| Os OO err) ar-scltaleletletelale = lale- eles! «le al aari+ olnle pergamentaceus. 
DD. Actinolateral membrane thick with short or moderately long actinolateral spines buried 
in it; spiracula moderately large in irregular groups of usually more than 10. 
ISL. geiflayergsll Kees) PYOEMEO Se Gon gob nao cp odd oS ODOR DOU ROR OOD ODO OOWOTDDE rhodopeplus. 
HE. Suboral spines thick, stout, sacculate.-..........5...- essen ere eee reer violaceus, 
AA. Adambulacral armature of more than one spine, 
