700 Proceedings of the Royal Irkh Academy. 
The interambulacral areas are rather more than four times the 
width of the ambulacra at their widest part, measuring 8-4 mm., 
the breadth of the ambulacra being 2 mm. There are two rows of 
seven and six primary tubercles respectively in each interambulacrum. 
The primary tubercles are of comparatively small elevation, perforate, 
and more or less distinctly crenulate on the abactinal side ; those 
near the apex being strongly crenulate ; and their mamelons are 
comparatively large, and almost hemispherical. The scrobicules are 
wide and transversely oval ; the scrobicular ring is incomplete in 
consequence of confluence with the adjacent scrobicules actinally 
and abactinally. There are from six to eight small mammillated 
miliary tubercles on each side, with an occasional small irregularly 
placed miliary granule here and there, but no other tubercles or 
granules are present on the plate, and consequently no miliary zone. 
In a favourable light, traces of faint radiating channels may be 
detected traversing the scrobicular area on the actinal side of the 
largest plates. The peristome is subpentagonal, 7'25 mm. in diameter, 
being about two-fifths of the diameter of the test, or 40 per cent. 
The buccal membrane is covered with imbricating scales. 
The apical system is large, measuring 8-5 mm. in diameter, or in 
the proportion of 47 per cent, of the diameter of the test. The genital 
plates are large and broadly shield- shaped. They are united by a 
rather broad contact, by which means all the ocular plates are shut 
out from entering the ring. The ocular plates are much smaller than 
the genital plates, and subpentagonal in shape, and their puncture is 
near the outer margin. I have not detected a puncture in any of the 
genital plates. There is, however, a well-defined round aperture 
amongst the periproctal plates, between the anal orifice, and one of the 
genital plates. The apical system as a whole is high and convex. 
The primary radioles are long and slender, cylindrical and tapering 
slightly; the longest measures 48-5 mm. in length, and a little less 
than 2 mm. in diameter. They are finely striated longitudinally, the 
ridges being very slightly prominent, and marked with very faint and 
indistinct serrations. There is a short collar above the milled rim, 
4 mm. in length, very finely and regularly striated, of a rich chocolate 
colour, in striking contrast to the ashy-white colour of the rest of the 
spine. The articulatory rim of the radioles above the ambitus is often 
strongly crenulate on one side in correspondence with the crenulated 
tubercle. 
The colour of the test in alcohol is of a rich purplish-brown or 
chocolate colour. 
