40 FOSSIL ASTEROIDEA. 
covered with small subregular hexagonal plates or paxillar tabule, which are, 
however, comparatively large for the size of the species. The primary apical 
plates are large and conspicuous, and all the plates in the central area of the disk 
and in the interradial areas are considerably larger than elsewhere; all diminish 
in size as they approach the margin of the disk. All the plates have their surface 
covered with a small, uniform, closely placed granulation, in which an indefinite 
subcircular arrangement in relation to the centre of the plate is discernible (see 
El ie 2d). 
The madreporiform body is small and subtriangular in outline ; its surface is 
sculptured by fine striations which radiate from the centre to the margin. The 
madreporite is usually enclosed by three plates, but four may be present in conse- 
quence of the division or retarded development of one of them, as is the case in 
the example figured on Pl. XIII, fig. 2c. The position of the madreporite is 
rather nearer the centre of the disk than the margin. 
The infero-marginal plates are at least six in number, counting from the 
median interradial line to the extremity,—that is to say, there are twelve (or 
perhaps more) for the whole side of the disk, as against eight in the supero- 
marginal series. The length of the three innermost plates on each side of the 
median interradial line is equal to that of the superior series, but there are three 
infero-marginal plates corresponding to the ultimate paired supero-marginal. As 
seen in the lateral wall of the disk, the height of the infero-marginal plates is greater 
than that of the supero-marginal series. The breadth of these plates, adjacent to 
the median interradial line on the actinal surface, is 5 mm. in an example whose 
minor radius measures about 15 mm. The breadth of the marginal border appears 
to be well maintained till near the extremity. The surface of the plates is 
ornamented in a similar manner to that of the supero-marginal plates, excepting 
that the punctations on the main area are rather more numerous, and that the 
finely punctate depressed border round the margin of the plate is much broader 
than in the plates of the superior series; the border is broader on the adcentral 
margin of the plate than elsewhere. (Compare figs. 3b and 4b on Pl. XIII.) 
The adambulacral plates appear to be comparatively small, but their preserva- 
tion in the examples examined is not sufficiently good to permit of description. 
The actinal intermediate plates, which are small and hexagonal, are covered 
with small, closely crowded, uniform granules. All are much displaced in the 
specimens under notice. 
Dimensions.—In the example figured on Pl. XIII, fig. 2a, the major radius is 
about 32 mm., and the minor radius about 25 mm. - The length of the side is 38 
mm. The thickness of the margin is about 8mm. In Forbes’s type (Pl. XIII, 
fig. 8 a) the major radius is about 20 mm., and the minor radius about 15°5 mm. ; 
