214 ME. "W. PEECy SLADEN ON THE 



I. suppose it would be impossible to prove that they actually 

 perceive colors ; but to suggest that the rays of various wave- 

 lengths produce on their eyes a different impression other than 

 that of color, is to propose an entirely novel hypothesis. 



At any rate, I think I have shown that they do distinguisli 

 between rays of different wave-lengths, and prefer those which 

 to our eyes appear green and yellow. 



The Asteroidea of H.M.S. ' Challenger' Expedition. — Part II. 

 By W. Peecy Sladen, F.L.S., P.G.S. 



[Eead May 3, 1883.] 

 [Published by permission of the Lords Commissioners of the Treasury.] 



Pamily Asteopecthstid^. 



Subfamily Poecellanasteeid^. 



Eays five, more or less produced. Marginal plates in superior 

 andinferior series, thin, lam elliform, apparently naked, or covered 

 only by an extremely thin epidermal tissue. Abactinal area 

 covered with membrane, beset with simple spiniferous spicules or 

 pseudo-paxillse, whicb occupy the whole or only a limited portion 

 of the area. A central epiproctal prominence, more or less 

 defined, frequently developed into an elongate tubular prolonga- 

 tion. Actinal interradial areas more or less extensive, paved 

 with thin squamiform ventral plates, more or less regularly 

 disposed and covered with delicate membrane. Adambulacral 

 plates elongate, simple, bearing spines (one to five in number) 

 on the furrow-margin only ; or may have one or more series of 

 small papilliform granules on the outer jDart of the plate. Cri- 

 briform organs along the vertical sutures of the marginal plates 

 in the interbracliial angles. Ambulacral sucker-feet in simple 

 pairs, with conical pointed tips. Madreporiform body placed 

 close to the marginal plates. 



