ASTEROIDEA OF NORTH PACUIC AND AD.JAC KNT WAIEKS — FISHER. 371 



KEY TO THE KNOWN SPECIES OF mPLOPTERASTER. 



a'. Central spine of pseudopaxillop projecting far beyond the othcn>, pivinR a very bri»llinK or i<piny 

 appearance to supradonal membrane; prominent furrow combs with fmir or five Hpine.-'; non- 

 prominent with three to five. 

 6'. PBeudopaxillce with eipht to ten spines; triangular moshes of supradnrsal reticulum with eiahl to 

 twenty spiracula; usually one Hpine less in the niinprDminenl furrow comb; lonpt-st adam- 

 bulacral spines and sacculus at leaat three times, sometimes four times, as long a.- base line of 



prominent combs muUipet (Sars), p. 371. 



6*. Peeudopaxillte with fifteen spines; triangular meshes with four or five spiracula; both kinds of 

 furrow combs with five spines; longest adambulacral spines and sacculus less than twice as long 



as the ba*ie line of the prominent combs (figure) I'orurtWtM (Sladen). 



a'. Central .spine of pseudopaxillic not protruding far beyond the rest and supradorsal membrane not 

 conspicuously spiny; five to ten paxillar spinclots; two or three spiracula to a mesh; prominent 

 furrow combs with seven or eight spines; alternate combs with five perfgrinator (.Sladen). 



Remarks. — The species tlc.scribed by Sladen are evidently very close to runll'i jieJi. 

 It is somewhat remarkable that no mention is made of this similarity. The iliffer- 

 ences outlined in the above synopsis may break down somewhnt when an ade<|uate 

 series of the southern forms is examined. It will not be sur[)risiiii^ if D. verriicoims 

 becomes a synonym of mitUipes, for the two are much alike. However, if tlie charac- 

 ters outlined by Slatlen hold constant, they can be kept distinct. Sladen's specimens 

 (number not designated) came from a single station, at the Atlantic entrance to the 

 Strait of Magellan, ho fathoms, sand. 



As to the validity of this genus, oi)ini()ns will, of course, differ. The characters 

 mentioned in the ditignosis are as important, surely, as those which sers'e to separate 

 Retaster from Ptera.tter. In fact, it is much ea.sier to draw the line between I>\plo}>- 

 teraster and Retaster, than between the latter and PtcraMer. 



DIPLOPTERASTER MULTIPES Sin). 



I'l. 107, figs. 1, 2. 



Pleraater muUipes Nf. Sars, Forh. Vid. Selsk. Christiania, 1805, p. 200; Fauna Litturalis Nor- 



vegia', pt. 3, 1877, p. (io, pi. 8, figs. 1-17. 

 Di pin pi (raster mullipes Verrili., .\mer. Joum. Sci., vol. 20, 1880, p. 400. 

 Retaster muUipts Sladen, Challenger Asteroidea, 1889, p. 477. 



Diagnosis. — Rays five, rarely six; general form stellato-pentagonal or very 

 broadly stellate, with depres.sed disk; actinolateral membrane broad ami fleshy 

 with free lateral border defining the ambitus; ambtilacra ver}' wide with large tube 

 feet in four rows; K = 92 mm., r=71 mm., H= l.;}±r: a small specimen, K= 1..52 r. 

 Supradorsal membrane tough, bristling with the prominent central spines of each 

 pa.xilla; paxilla^ with long pedicels surmounted by a prominent stout central sjiine 

 anil seven to nine slender shorter radiating peripheral spines, the tip of each being 

 joined to that of central s])ine, and also together, by a muscular band, the thinner 

 membrane between being i)ierced by about eight to twenty spiracula. the spiraciilar 

 areas thus are radially disjiosed about the prominent central spine of each |)axilla; 

 osculum large. Adambulacral ])lateswith twokinds of combs. one jirojecting farther 

 into furrow than the other; promiiicnl combs with four or five webbe<l spines; 

 non|)rominent with three or four; web prolonged Innond tips of longer spines as a 

 long (lap or sacculus. Oral spines four or live (rarely six on onesided slender, the 



