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



of suture. Their marginal armature has the appearance of forming three distinct fans, 

 one at the inner extremity of the united pair of plates, and one on each plate laterally. 

 The former is composed of the innermost five or six spines of each plate, which are robust, 

 elongate, the one or two outer ones being smaller than the others, and they are united for 

 about a third of their length by a membranous web, which extends uninterruptedly upon 

 and covers the plate. The lateral combs are composed of about thirteen spinelets, which 

 are shorter and very much more delicate than those in the buccal comb, and increase in size 

 as they recede from the mouth, until near the outer extremity, when they again diminish 

 in size. These spinelets are also webbed at the base like the buccal comb. On the flanks 

 of the median keel there is a lineal series of four or five short conical spines on each plate, 

 running parallel to the median suture, which diminish in size as they recede from the 

 mouth. No other spines are borne on the mouth-plates. The actinostome is very large 

 and widely open. 



I have not been able to detect any supplementary intermediate plates in the inter- 

 radial regions, in addition to those of the regular continuous longitudinal series above 

 described. 



The madreporiform body is rather small, transversely oval, slightly convex, and is 

 situated near the margin. The striae are remarkably fine and numerous. 



The anal aperture is excentric and difficult to detect ; two or three neighbouring 

 paxillae trend over the aperture, but are not modified in form in any way. 



The ambulacral furrows are rather narrow in comparison to the size of the starfish. 

 The tube-feet, which are arranged in two regular rows, have large, fleshy, centrally invagi- 

 nated, terminal disks. 



I have not detected the presence of pedicellariae of any kind. 



Colour in alcohol, a light yellowish brown, the paxillae being a bleached ashy white. 



Locality. — Station 188. In the Arafura Sea, between Cape York and Frederick Henry 

 Island. September 10, 1874. Lat. 9° 59' 0" S., long. 139° 42' 0" E. Depth 28 fathoms. 

 Green mud. Surface temperature 78° - 5 Fahr, 



Genus Solaster, Forbes. 



Stellonia {pars), Agassiz, M6m. Soc. Sci. Nat. Neucliatel, 1835, t. i. p. 191. 



Solaster, Forbes, Mem. Wern. Soc., 1839, vol. viii. p. 120. 



Crossaster (pars), Midler and Troschel, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 1840 (April), 



p. 103. 

 Solaster (subgenus Endeca), Gray, Ann. and Mag. Nat. Hist., 1840 (November), vol. vi. p. 183. 



The genus Solaster, like Crossaster (with a single exception), was hitherto known 

 only from the northern hemisphere. The new species obtained by the Challenger from 

 the Pacific and Southern Oceans indicate a wide area of distribution. The bathymetrical 

 range of Solaster is greater than that of the allied genus Crossaster. The discovery of 



