The Echinoderm Fauna of South Africa. 265 



all the larger abactinal plates and many small ones too, bear a single, 

 central blunt spine, 1-3 mm. long and about I j 2 mm. in diameter; 

 not rarely the spine, on the smaller plates, is replaced by a large 

 non-denticulate spatulate-j awed pedieellaria; on the larger plates, spine 

 and pedicellaria may both occur. Madreporite large, tumid, about 

 3 mm. in diameter and 12 mm. from the disk margin. 



Supermarginal plates 16 on a side, bare and tumid; the proximal 

 are squarish and about as long as wide but distally the plates become 

 much wider than long ; each plate (except near tip of ray) carries 2, 

 and sometimes 3, stout spines like those on the abactinal plates; 

 these are placed one above the other ; besides these spines one or 

 more coarse granules or small tubercles may be present or, occasion- 

 ally, one or even two pedicellariae occur instead of the tubercles; 

 the usual series of marginal granules surrounds each of the plates. 

 Terminal plate quite small, swollen and with no spines or tubercles 

 whatever; it is possible that these may have been present in life and 

 have since been knocked oft' but if so they have left no scars. Infero- 

 rnarginal plates 17 on each side, the basal ones longer than wide and 

 longer than the corresponding superomarginals, but distally they 

 decrease in length rapidly and an extra one is intercalated below the 

 twelfth of the upper series, or thereabouts; these plates carry 2-5 

 spines in a central group, or in a vertical or horizontal series; the spines 

 are similar to those of the upper plates, and like them may be 

 accompanied by pedicellariae. Actinolateral plates in six or seven 

 series, the first parallel to the adambulacrals and reaching as far as 

 the seventh inferomarginal ; the second series does not quite reach 

 the fifth inferomarginal ; the remaining series are confined to the 

 disk ; each plate is surrounded by the usual marginal granules and 

 these also occur more or less abundantly on the surface of the larger 

 plates, especially near the mouth ; each plate, excepting only the 

 small ones, carries a large, central spine, similar to those of the 

 abactinal surface but perhaps a little bigger; on some of the plates, 

 the large characteristic pedicellariae occur. 



Adambulacral plates 57 in each series but 21 of these are on the 

 last 18 mm. of the arm ; there are 6-9 (usually 8 or 7) slender 

 compressed spines on the furrow margin, which are subequal or the 

 end ones may be much the smallest; on the surface of the plate are 

 2 large spines, placed one behind the other, and on the adoral, inner 

 corner there is usually a big pedicellaria; the plates are surrounded 

 by the usual marginal granules and a number of these occur on the 

 face of the plate, particularly around the base of the outer spine. 

 Oral plates long and narrow, but not swollen; on the free margin 



