326 THE VOYAGE OF H.M.S. CHALLENGER. 



Genus Leptogonaster, Sladen. 

 Leptogonaster, Sladen in Narr. Chall. Exp., 1885, vol. i. p. 616. 



Disk large, thin, pentagonal, capable of slight inflation. Kays moderately elongate, 

 flat, broad at the base, tapering gradually to the extremity, and producing a widely 

 rounded interbrachial arc. The whole abactinal area covered with a uniform granulation 

 imbedded in membrane. 



Marginal plates forming a well-defined border to the disk and rays, presenting a 

 bevelled angular margin in the interbrachial arc, but a vertical wall on the outer half of 

 the ray. The supero-marginal plates bear no spines. The infero-niarginal plates bear on 

 the bevelled angular margin in the interbrachial arc a longitudinal series of four or five 

 short conical spinelets, which do not extend beyond the disk ; along the ray, the infero- 

 marginal plates bear a small tubercle or aborted spinelet, which becomes more definitely 

 developed towards the extremity. 



Abactinal area of the disk, which may be more or less inflated in the radial regions, 

 covered with flat polygonal plates, overlaid with a uniform granulation imbedded in 

 membrane. Papulae numerous. Small, elongate, two-jawed pedicellarise present here 

 and there. 



Adambulacral plates large and long: armature consisting of: — (1.) On the furrow 

 margin a series of five to seven short, delicate spinelets, partially united by a membranous 

 web and arranged in a semicircular comb. (2.) On the actinal surface, a single long pedi- 

 cellaria at the adoral extremity ; and two short conical spinelets standing side by side. 



Actinal interradial areas covered with thin hexagonal intermediate plates, usually 

 granulous, overlaid with a continuous layer of membrane. The plates adjacent to the 

 adambulacral plates each bear a small valvate pedicellaria, resembling a subpapilliform 

 tubercle. Small indistinct granules are present on the plates. Occasionally an incon- 

 spicuous pedicellaria is present on the plates in the inner series of intermediate plates. 



Madreporiform body large and situated rather nearer the centre of the disk than mid- 

 way on the interradial line. 



Anal aperture subcentral. 



Ambulacral tube-feet with a well-developed sucker disk. 



Remarks. — I have been in considerable doubt as to the retention of this genus after 

 the publication of M. Perrier's 1 memoir on the starfishes collected by the "Blake" 

 Expedition. The figure given by him of Anthenoides piercei, 2 which is an indistinct 

 photo-lithograph, led me to think that the present starfish and the "West Indian one 

 dredged by the "Blake" were congeneric forms; but it is expressly stated by Perrier in 



1 Nouv. Archives Mas. Hist. Nat, 1884, 2e Sene, t. vi. pp. 127-276. 



2 Op. cit, pi. viii. fig. 1. 



