54 FOSSIL ASTEROIDEA. 
merges in the rounding of the high lateral wall of the plate. On the level area 
of the plate, which is consequently the inner or adcentral part of the surface, are 
several low tubercular eminences of irregular shape and disposition, but which 
appear to assume a more or less distinct biserial arrangement at right angles to 
the adcentral margin of the plate. They appear to be enlarged irregular granules, 
and in all the examples I have examined they have become to a certain extent 
ill-defined, owing either to growth or to weather-wearing. The general character 
of the ornamentation is shown in Pl. XIV, fig. 4c. The entire margin of the 
plate is surrounded by a very narrow depressed border, which is very minutely 
punctate, probably only in a single lineal series. The general superficies of the 
plate beyond the ornamentation mentioned is smooth, as if weatherworn, in all 
the examples I have seen, but in some specimens there appear to be traces of a 
more or less granulous character, and in some instances suggest the impression 
that an ornamentation similar to that noticed in Mitraster rugatus was probably 
present on at least a part of the surface of the plate. The height of the supero- 
marginal plates as seen in the margin is greater than their length, and their 
prominent abactinal tumidity has a distinctly conical character from this point 
of view. 
The ultimate paired plate is fully twice as long as the other supero-marginal 
plates measured on the outer margin, and its breadth is equal to that of the 
adjacent supero-marginal. It is triangular in form, and the line of junction with 
the companion ultimate plate of the adjacent side coincides with the median 
radial line. The actual dimensions in the example under description are, length 
6-2 mm., breadth about 6 mm. As seen in the lateral view of the disk the 
ultimate plates are distinctly tumid abactinally (see Pl. XIV, fig. 46). The 
abactinal surface of the plate is ornamented by a number of miliary tubercles or 
granules, more or less serially disposed parallel to the margin adjacent to the 
companion plate, and more numerous at the adcentral end of that margin. 
Beyond this the surface of the ultimate plate is smooth, like that of the other 
supero-marginal plates. 
The abactinal area of the disk within the boundary of the marginal plates is 
covered with hexagonal or polygonal plates or paxillar tabule, which are small in 
size generally, excepting the primary apical plates, which are comparatively very 
large. All the plates have their surface covered with a fine, uniform granulation. 
The primary apical plates have a small central area of low elevation, not higher 
than if a number of granules had become coalesced—the structure being sugges- 
tive of a tubercle in process of disappearance,—in other words, the scar left by a 
tubercle which had existed in an earlier stage of growth (see Pl. XIV, fig. 4d). 
Dimensions.—The example figured on Pl. XIV, fig. 4a, has the following 
