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



near the extremity of the ray. In Nymphaster albidus the rays appear to be com- 

 paratively narrower at the base and consequently more slender, and they taper less 

 gradually. 



Locality. — Off the Cape Verde Islands. (Exact position and conditions not re- 

 corded.) 



5. Nymphaster basilicus, n. sp. (PI. LVIT. figs. 8 and 9). 



I have felt obliged to place a single example of Nymphaster dredged at Station 125 

 as a distinct species. The size of the specimen denotes a large robust form, but unfortu- 

 nately in the present case each of the rays had suffered mutilation during life, and four of 

 them are now represented only by dwarfed and imperfectly grown reproductions ; it is 

 consequently impossible to give accurately the measurement of the major radius or the 

 number of the supero-marginal plates. The minor radius measures 28*5 mm. ; and judg- 

 ing from a ray which has been mutilated, but not entirely removed, as in the case of the 

 other four, the major radius was about 91 mm. or more, for the extremity even in this ray 

 is not absolutely perfect. 



The plates of the abactinal paxillar area are regularly hexagonal, those of the radial 

 regions are nearly uniform in size in the respective series, and diminish slightly as they 

 proceed outward. All are definitely and uniformly spaced slightly apart, the isolated and 

 regularly placed papulae being visible. The plates of the interradial regions, on the other 

 hand, are smaller and closely crowded ; and from the fact that they diminish in size as 

 they approach the margin of the disk, the plates, which are arranged in longitudinal 

 series parallel to the median radial series, also appear to fall into series obliquely trans- 

 verse, passing from the median line to the margin of the disk, towards which they converge 

 slightly in consequence of the decrease of size above mentioned. Nearly all the larger 

 plates carry one of the small pedicellarise in a pit, always placed near the margin of the 

 plate, and rarely two are present. The dorso-central plate and its surrounding circlet of 

 plates, which intervene between it and the basals and under-basals, are large and distinct. 

 The anal aperture lies external to the dorso-central plate, and the madreporiform body is 

 independent of, and lies external to, its adjacent basal plate, which is rather smaller. 

 There is a little depression in the triangular interradial regions which gives a slight appear- 

 ance of convexity to the radial regions. 



In the armature of the adambulacral plates, the furrow series of spinelets accords with 

 those already described in Nymphaster protentus, but there is no external series of spine- 

 lets as in that form, the whole of the outer portion of the plate, which is large, being 

 covered with numerous small semiglobular granules, uniform in all respects with those on 

 the actinal intermediate plates. The granules usually fall into three or four subregular 

 longitudinal lines, but some of these may be angulated, and there is often considerable 



