48 FOSSIL ASTEROIDEA. 
Body rather small, or at most only of medium size. General form depressed. 
Abactinal surface flat, or with a tendency for the rays to be slightly directed 
upward at the extremities. Actinal surface slightly convex. Marginal contour 
pentagonal, with the sides slightly lunate, though the curvature is often more or 
less flattened; the extremity of the rays is only slightly produced. The major 
radius measures about one-third more than the minor radius, the major dimension 
being proportionately rather greater in large tests than in small ones. The 
margin is thick, and the lateral wall has more of a precipitous than a rounded 
character, although the infero-marginal plates are well rounded on the actinal 
surface. 
The supero-marginal plates are three in number, counting from the median 
interradial line to the extremity, or six from the tip of one ray to the tip of the 
adjacent ray, exclusive of the odd terminal or “ ocular’ plate in each case. They 
form a broad border to the abactina! area of the disk, of uniform breadth through- 
out, which measures about 7 mm. at the median interradial line in an example 
whose major radius measures 36°5 mm. and minor radius 27 mm. (Pl. XIV, fig. 2 a). 
Excepting the ultimate paired plates, the four intermediate supero-marginal plates on 
each side of the disk are of equal size, the breadth being about once and a half the 
length, the actual measurements in the specimen under notice being length 5 mm., 
and breadth 7mm. ‘The abactinal surface of these plates is tumidly convex, while 
the lateral wall is plane and vertical, and the abactinal tumidity commences 
abruptly at a little distance from the adcentral margin of the plate, which leaves a 
small level area at the rounded end of the plate abutting on the abactinal plates or 
paxillar tabule. On the surface of this level band near the adcentral margin, and 
forming a more or less definite series running parallel to it, are three or four 
irregular tubercular eminences or granules, but very indistinct and more or less 
weatherworn (see Pl. XIV, fig. 2c). The entire margin of the plate is surrounded 
by a very narrow depressed border, with very fine, closely crowded, uniserially 
disposed punctations, upon which a small miliary granulation was previously borne. 
The whole general superficies of the plate is smooth and weatherworn in every 
example I have seen. The height of the plates as seen in the margin is as great 
as or even slightly greater than their length, and the prominently tumid character 
of the plates abactinally causes them to appear in the lateral view somewhat like 
truncate cones abruptly rounded (see Pl. XIV, fig. 20). 
The ultimate paired plate is larger and longer than any of the other plates, 
and is of a different and very peculiar shape. It is subtriangular in form as seen 
from above, produced and pointed at the extremity, and to a certain extent recalls 
the form of a ploughshare or coulter in consequence of a peculiar nipped-in 
appearance caused by the extension of a tumid region which runs parallel to the 
