248 



THE VOYAGE OF H.M.S. CHALLENGER. 



Luidia debilis of Grube has only the indefinite locality of " Africa.' The single type- 

 specimen is so small that it might be anything, and is quite unworthy of being maintained 

 as the type of a species. I therefore consider that the name should be discarded. 



Chorological Synopsis of the Species herein described. 



1. Luidia aspera, n. sp. (PI. XLIII. figs. 1 and 2 ; PI. XLV. figs. 9 and 10). 



Pays eight to ten. R = 170 mm.; r = 20 mm. (R = 168, r = 19). R = 8'5r. 

 Breadth of a ray at the widest part near the base, 16 to 17 mm. 



Rays elongate in relation to the size of the disk, thick, robust, of a slightly depressed 

 subcylindrical form, constricted for a short distance near the base, then tapering from the 

 widest part slowly and gradually up to the pointed extremity. Abactinal surface convex, 

 but flattened along the median radial line and upon the disk. Actinal surface rounding 

 gradually to the margin. Lateral walls rounded. 



The paxillae of the abactinal area are large, rotund in form, but with a more or less 

 subquadrangular facies in the regular longitudinal series, which are six in number at each 

 side of the ray. In the comparatively narrow intermediate area along the median radial 

 line the paxillae are slightly smaller, distinctly rotund, crowded, and irregular in disposi- 

 tion. Nearly all the paxillae of the innermost three longitudinal rows (at least on the 

 inner half of the ray), have a robust subconical spinelet about l"5-2 mm. in length on the 

 centre of the tabulum. This is surrounded by about eight very small, cylindrical, 

 obtusely-rounded, papilliform spinelets likewise placed on the tabulum, often faintly sub- 

 clavate, and so short that they are little more than elongate granules. External to these 

 and at the margin of the tabulum is a series of about two dozen similar but slightly more 

 delicate and slightly longer spinelets. Excepting of course the central large one, the 

 spinelets on the tabulum and the marginal series all appear of equal height when drawn 

 together. Occasional paxillae in the three rows mentioned are devoid of the central 

 conical spinelet, especially on the outer part of the ray, where not more than two of the 

 longitudinal series have echinulated paxillae. The large paxillae between the echinulate 



