60 FOSSIL ASTEROIDEA. 
specimen under notice being length 4 mm. and breadth 6:3 mm., in the plate 
adjacent to the median interradial line. The length of the plate at the end which 
falls in the margin of the disk is a shade greater than the adcentral or inner end, 
and the plates are consequently faintly wedge-shaped, but so slightly that the 
character is scarcely noticed at first sight. The ultimate plates, however, are 
distinctly wedge-shaped, the length at the outer margin being a little greater 
than that of the other marginal plates, while the length of the mner end is rather 
less—often not more than one-half the length of the same end in the other plates. 
The breadth of the ultimate plates is the same as that of all the supero-marginal 
plates ; and the corresponding plates of the two adjacent sides touch one another 
throughout, the line of junction falling in the median line of the ray. The abactinal 
surface of the plates is distinctly convex, and the character is more conspicuously 
emphasised by the plate becoming rapidly gibbous on the outer half, the outer 
side of the eminence forming the rapid bend to the lateral wall of the plate. 
The height of the plates as seen in the margin is usually equal to, or even 
rather greater than their length, but may occasionally be less. There is no 
diminution in height as the plates approach the extremity of the ray, and the 
ultimate paired plate has a tendency to appear even a trifle higher and more 
gibbous than the others, but the character is derived probably more from the 
position in which the plate sometimes is than from an actual increase in size or 
gibbosity. The abactinal surface of the plates is covered with coarse tuberculiform 
mamunillations which gradually die out before reaching the apex of the gibbosity. 
In the interspaces between the eminences are small, more or less widely spaced 
punctations, and these extend over the whole surface of the plate, and are 
consequently present on the outer portions as well as on the lateral wall. There 
is a narrow depressed border round the entire margin of the plate, which is very 
minutely punctate (see Pl. XII, fig. 3c). In smaller examples there often appears 
to be only one or two rows of punctations. The ornamentation of the ultimate 
paired plates is precisely similar to that on the other supero-marginal plates. 
The odd terminal or ‘ocular’ plate is very small, and, so far as I can make 
out, resembles superficially a short truncated cylinder which protrudes somewhat 
cannon-like from a small triangular space left by the ultimate paired plates similar 
to what I have already described in Metopaster. 
The abactinal area of the disk within the boundary of the marginal plates is 
covered with comparatively large polygonal plates, with closely crowded, rather 
coarse, uniform granulations, upon which miliary granules or spinelets were 
previously borne. ‘he primary apical plates are remarkably large, and the plates 
in the interradial areas are larger than the plates in the radial areas. Of the 
plates in the radial areas at least the median series and two series on each side 
have bases of a six-rayed, substellate form. These are admirably seen in an 
