ASTEKOIDEA OF H.M.S. ' CHALLENGER ' ESPEDITION. 267 



the ray. Inner series three in number, short, cylindrical or flat- 

 tened transversely, slightly taper, the middle one a little longer than 

 the companion spines and standing forward prominently in the 

 furrow. The second series has usually two spines standing wide 

 apart, opposite the two outer spines of the furrow-series ; these 

 spines are shorter than the inner trio, flattened in the plane of 

 the axis of the ray, do not taper, and are roundly truncate at the 

 extremity. Sometimes a third spinelet, similar in size and shape, 

 is present between them. The outer series consists of three 

 small papilliform spinelets, only slightly longer and more robust 

 than the transitional or ciliary spinelets abore mentioned. 



Mouth-plates small and narrow, with a single line of rather 

 long compressed spinelets, standing perpendicular to the super- 

 ficies, excepting those near the inner extremity, which are directed 

 horizontally over the mouth and are also larger and more robust ; 

 those at the outer extremity are directed outwards. Low down 

 on the sides are a few small and irregular supplementary spines. 

 The paxHlar area is very limited in consequence of the great 

 breadth of the supero-marginal plates. The paxillse are large 

 upon the disk, but become smaller along the rays ; the former 

 have four or five rather large granules in the centre on the tabu- 

 lum, surrounded by a dozen or more small short spinelets. Along 

 the rays there are not more than two or three central granules, 

 and these are arranged in line, the paxilla (tabulum) being more 

 or less elongately oval in the direction of the axis of the ray. 

 The paxillae are closely placed. In the centre of the disk a small 

 conical elevation is present, upon and in the neighbourhood of 

 which the paxillse are smaller. 



The madreporiform body is about its own width distant from 

 the marginal plates, and is almost hidden from view by the 

 paxillse. 



Colour, in alcohol, almost pure white. 



Station 122. Lat. 9° 5' S. to 9° 10' S., long. 34° 49' "W. to 34° 

 53' W. Depth 350, 120, 32, and 400 fms. ; mud. 



There is, unfortunately, no indication as to which of these 

 dredgings the specimen came from. 



ASTEOPECTEN MESACTUS, n. sp. 



Rays five. i2 = 3r; i2=34 millim., r = ll millim. Disk of 

 moderate size and somewhat tumid ; rays rather short and mode- 

 rately broad at the base, tapering continuously to a finely pointed 



