KEPOKT ON THE ASTEKOIDEA. 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 thin ' intermediate 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 l ) in number in each interbrachial arc. 



Synopsis of the Species included in the Genus Hyphalaster herein described. 



A Five cribriform organs in each arc. Abactinal area with prominent groups of paxillai . diadematus. 



B. Seven cribriform organs in each arc. No prominent groups of paxillre 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-paxillae. 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. 

 h. Disk with fully developed paxilhe. 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 2 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 Expedition. 

 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 {Joe. cit, p. 886) by M. Perrier :— " Les Hyphalaster (Hyphalaster 

 Antonii, E. P., Hyphalaster Parfaiti, E. P.) ont leurs plaques adambulacraires de 

 forme normale, et non pas obliques, par rapport a la gouttiere 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 dernieres se soudent h leurs 

 sym^triques ; le second a neuf organes cribriformes." 



1 Fide Perrier, Comptes rendus, 1885, t. ci. p. 886. 



2 Cumptes rendus, 1885, t. ci. p. 886. 



