REPORT ON THE ASTEROIDEA. 155 
less defined in the centre of the disk, similar to that present in some species of Astro- 
pecten, but is usually more conspicuously developed, although it does not attain the 
tubular form of this appendage found in Porcellanaster. 
Actinal interradial areas extensive, paved with numerous thinfintermediate plates 
arranged in regular columns and imbricating. 
Ambulacral furrows narrow and concealed. Armature of the adambulacral plates 
consisting of short compressed spines, three to five in number, usually forming a kind 
of fan or independent series on each plate. 
Cribriform organs five to seven (or nine‘) in number in each interbrachial are. 
Synopsis of the Species included in the Genus Hyphalaster herein described. 
A. Five cribriform organs in each arc. Abactinal area with prominent groups of paxille . diadematus. 
B, Seven cribriform organs in each are. No prominent groups of paxille on the abactinal 
area. 
a, Supero-marginal plates meet in the median line. Cribriform organs very narrow. 
Secondary row of granules behind the furrow series of spines on the adam- 
bulacral plates aborted or absent. 
a. Disk with very imperfect pseudo-paxilla. Two innermost supero-marginal plates 
on each side of the median interradial line with small spinelets. Mouth- 
plates with secondary mouth-spines. Body frame very thin and delicate . hyalinus. 
6. Disk with fully developed paxillz, No spinelets on the supero-marginal plates. 
No secondary mouth-spines, Body frame robust and rigid . : ‘ : inermis. 
b. Supero marginal plates not united in the median line. A series of small secondary 
granules behind the furrow series of spinelets in" the armature of the adam- 
bulacral plates. Cribriform organs very broad and expanded . ! : : planus. 
M. Perrier? mentions by name two starfishes which he refers to Hyphalaster, 
dredged in the Atlantic during the “Talisman” Expedition, from 2995 and 4787 metres 
respectively. This is an interesting extension of the range of the genus, as no repre- 
sentatives of it were found in the Atlantic during the Challenger LExpedition. 
Unfortunately no descriptions of the species are given, and I am therefore unable to 
compare them with the present series. The following is the only information respecting 
them given (loc. cit., p. 886) by M. Perrier :—“ Les Hyphalaster (Hyphalaster 
Antoni, E. P., Hyphalaster Parfaiti, E. P.) ont leurs plaques adambulacraires de 
forme normale, et non pas obliques, par rapport & la gouttiére qu’elles bordent; le 
premier a sept organes cribriformes, dont deux rudimentaires, mais il y a, pour chaque 
bras, neuf plaques marginales dorsales dont les quatre derniéres se soudent 4 leurs 
symétriques ; le second a neuf organes cribriformes.” 
1 Fide Perrier, Comptes rendus, 1885, t. ci. p. 886. 
2 Comptes rendus, 1885, t. ci. p. 886. 
