692 Proceedings of the Royal Irish Academy 
the breadth. The ultimate plate is small and corresponds with the 
ultimate supero-marginal plate. The infero-marginal plates bear 
precisely similar granules to those on the superior series, their 
presence now being similarly confined to the lateral area, and the 
single series surrounding the margin. On the naked portion of the 
actinal surface of the plate large isolated pits occur, and occasionally 
a granule is present therein. I have detected no pedicellariee on 
either series of marginal plates. 
The adambulacral plates are slightly longer than broad, and their 
armature consists of three regular series ; the first or furrow series 
being true spinelets, whilst the second and third, which are on the 
actinal surface of the plate, are only granules. In the furrow series 
are five or six short obtuse cylindrical spinelets which are directed 
over the furrow, the adoral spinelet of the series being often placed 
further back on the plate than the others, and it is sometimes also 
much smaller. The second and third series consist of a longitudinal row 
of four or five granules, the outer series being similar to the granules 
on the actinal intermediate plates, and the second series only slightly 
more elongate or papilliform. I have found no pedicellarise on the 
adambulacral plates, in fact nowhere on this example at all. 
The mouth -plates are small, but fairly conspicuous. Their 
armature consists of a marginal series on each plate of eight spinelets 
similar to the marginal or furrow series on the adambulacral plates, 
the innermost spinelet being rather larger than the others, and 
subprismatic. On the actinal surface of the plate is a longitudinal 
series of eight granules parallel to the suture which unites the two 
mouth-plates of an angle ; a series of four granules parallel to the 
margin adjacent to the adambulacral plates ; and an intermediate 
series, also of four granules, traversing the surface of the plate between 
these two series. The granules in each of these series become slightly 
more papilliform as they approach the free margin. 
The actinal interradial areas are paved with small, normally 
rhomboid but occasionally polygonal, intermediate plates. They are 
arranged in series parallel to the ambulacral furrow. The plates of the 
series adjacent to the adambulacral plates are slightly larger than the 
others, and this series, which is the longest, does not extend beyond 
the third infero-marginal plate, counting from the median interradial 
line. The surface of the plates is covered with small, low, uniform 
granules, which are well spaced, and exhibit no arrangement excepting 
the series which marks out the margin. 
The ajjal orifice is slightly excentric, and is surrounded by 
