478 



THE VOYAGE OF H.M.S. CHALLENGER. 



/3. Bathymetrical range : 6 to 640 fathoms. 



Greatest range of one species : Retaster multipes, 124 to 640 fathoms. 

 All the other species whose depth is known are confined to the Littoral zone, 

 with the exception of Retaster gibber, which extends into the Continental zone. 

 y. Nature of the Sea-bottom : Retaster multipes occurs, on greenish clay ; Retaster 

 verrucosus on Sand ; Retaster peregrinator on Volcanic mud ; Retaster gibber 

 on Blue mud ; Retaster insignis on Coral mud and Green mud. 

 The species collected by the Challenger are indicated in the above list by an asterisk. 



Chorological Synopsis of the Species. 



1. Retaster verrucosus, Sladen (PI. LXXVI. figs. 1 and 2; PL LXXVII. figs. 9 and 10). 

 Retaster verrucostis, Sladen, 1882, Journ. Linn. Soc. Lond. (Zool.), vol. xvi. p. 196. 



Marginal contour moderately indented in the interradia, which are angular and not 

 rounded ; outline of the rays gracefully curved outwards. The minor radius is in the 

 proportion of 59 "5 per cent. R = 47 mm.; r = 28 mm. Abactinal profile moderately 

 high and rounded, tapering gradually to the extremity of the rays, which are slightly 

 upturned and expose the ambulacra! furrow on the abactinal area. Actinal surface flat. 



The supradorsal membrane is very regularly and uniformly reticulated. The paxillse 

 have long pedicles, and bear a crown of about fifteen spinelets, nearly as long as the 

 pedicle. The central spinelet, which is very much more robust and longer than any of the 

 rest, stands perpendicular, rising in the centre of the mesh, whilst the others, which are 

 slender and delicate, radiate round it and outward to the fibrous bands that form the 

 outline of the mesh. The median spinelet is much more prominent than any of the others ; 

 and the thick fleshy cap formed upon it by the supradorsal membrane imparts a very 

 conspicuous papillate appearance to the starfish, assuming in large specimens almost a 

 semi-tuberculate character of great regularity and evenness of disposition. In fully grown 

 specimens the whole membrane becomes very thick and wrinkled, rendering it difficult to 

 trace the radiating bands ; in moderate-sized specimens, however, they may be clearly 

 distinguished without removing the epidermis. From the central spinelet six to eight 



